Evidence library
Vehicle issues from the 19-book series
Search real book scenarios by symptom, vehicle, evidence type, or outcome. These cards preserve the distinction between a scanner finding, a diagnostic check, and a condition the scanner could not see.
148issue records
9recurring patterns
9reader-friendly groups
19book perspectives
Readiness monitors incomplete on a dealer lot car
- Vehicle or context
- Used sedan, dealer lot
- How it was handled
- Fast self-tests complete and slow ones not ready means a recently cleared memory. Asked one question on the spot rather than making an accusation, and had the answer written on the file
- Discussed in
- To Buy A Car
Seller denied a fault the vehicle had recorded
- Vehicle or context
- 2019 Chevrolet Traverse, private sale
- How it was handled
- Stored fault read at the viewing contradicted the seller's account. Vehicle rejected on the mismatch rather than on the fault itself
- Discussed in
- To Buy A Car
California smog readiness rules
- Vehicle or context
- Any 2000 or newer vehicle
- How it was handled
- Only the evaporative monitor may be incomplete. Any other incomplete monitor is a fail, which makes a recently cleared memory a smog problem as well as an honesty problem
- Discussed in
- To Buy A Car
Hybrid battery module data not reachable
- Vehicle or context
- 2017 Toyota Highlander Hybrid
- How it was handled
- Scope boundary. Block-level battery data needs a manufacturer app and an adapter that can address individual modules. Negotiated, then walked on price
- Discussed in
- To Buy A Car
Live data on a test drive
- Vehicle or context
- All candidates
- How it was handled
- Passenger reads the screen, never the driver. Coolant behaviour, fuel trims and misfire counters watched across a route rather than glanced at once
- Discussed in
- To Buy A Car
Odometer credibility
- Vehicle or context
- All candidates
- How it was handled
- Module-reported distance cross-checked against the dashboard and the paperwork
- Discussed in
- To Buy A Car
Dating a fault to before or after a viewing
- Vehicle or context
- All candidates
- How it was handled
- Freeze frame conditions recorded with each stored fault
- Discussed in
- To Buy A Car
Open safety recalls
- Vehicle or context
- All candidates
- How it was handled
- Free VIN lookup at the national recall database, done before driving anywhere
- Discussed in
- To Buy A Car
Condition items no scanner reaches
- Vehicle or context
- 2018 Honda Odyssey
- How it was handled
- Paid pre-purchase inspection on a lift found about $1,100 of work that no screen had reported. Deducted from the price
- Discussed in
- To Buy A Car
Tyre age against tread depth
- Vehicle or context
- All candidates
- How it was handled
- Manufacturing date codes read off the sidewalls. Full tread on an old tyre is not a good tyre
- Discussed in
- To Buy A Car
Service code 13, intake air temperature circuit
- Vehicle or context
- Ninja 400
- How it was handled
- A connector left unclipped after a do-it-yourself air filter change. Reseated, code cleared through the factory three-cycle ride procedure
- Discussed in
- To Fix A Bike
Service code 33, oxygen sensor
- Vehicle or context
- Ninja 400
- How it was handled
- A secondhand slip-on exhaust leaning the mixture. Original exhaust refitted rather than using any of three illegal workarounds offered online
- Discussed in
- To Fix A Bike
Service code 11, main throttle sensor
- Vehicle or context
- Ninja 400
- How it was handled
- Water in a connector plug after a storm. Dried, cleaned and reseated
- Discussed in
- To Fix A Bike
Service code 31, vehicle-down sensor
- Vehicle or context
- Ninja 400
- How it was handled
- A low-speed tip-over. The sensor doing exactly its job. Reset, and the start interlock chain understood rather than feared
- Discussed in
- To Fix A Bike
Charging system collapse at night
- Vehicle or context
- Ninja 400
- How it was handled
- Caught from a recorded voltage trace on a dark road because twelve months of monthly readings existed to compare against. Regulator and rectifier replaced
- Discussed in
- To Fix A Bike
Service code 39, ECU communication
- Vehicle or context
- Ninja 400
- How it was handled
- A battery terminal loosened by vibration. Cleaned and tightened
- Discussed in
- To Fix A Bike
Service codes 24 and 25, wheel rotation and gear position
- Vehicle or context
- Ninja 400
- How it was handled
- A sprocket and gearing change altering the ratio the machine expected. Diagnosed against a friend's confident but wrong theory
- Discussed in
- To Fix A Bike
Reading codes without a tool at all
- Vehicle or context
- Ninja 400
- How it was handled
- The instrument panel displays stored codes free with a button sequence. The tool's value is clearing, live data and logging, not the code itself
- Discussed in
- To Fix A Bike
Items with no code at all
- Vehicle or context
- Ninja 400
- How it was handled
- Scope boundary. Tyre age, brake fluid moisture, a chain tight spot and a weeping fork seal, all found by an independent mechanic in forty minutes
- Discussed in
- To Fix A Bike
Recently cleared memory at a consignment lot
- Vehicle or context
- Camper-era consignment machine
- How it was handled
- Fast tests complete, slow tests not ready. Established on the spot as a battery fitted nine days earlier, and written onto the file
- Discussed in
- To Buy A Pre-Owned Bike
A warm engine at a viewing
- Vehicle or context
- Private sale machine
- How it was handled
- Asked for the machine to be left unstarted and returned on a Saturday. Cold-start counters and trims read clean
- Discussed in
- To Buy A Pre-Owned Bike
Exhaust flap actuator fault
- Vehicle or context
- 2019 BMW S 1000 XR
- How it was handled
- A butterfly valve seized in its bore after three years standing. Freed, cleaned and tested. The dealer quote had proposed the complete exhaust assembly
- Discussed in
- To Buy A Pre-Owned Bike
Ride height signal implausible
- Vehicle or context
- 2019 BMW S 1000 XR
- How it was handled
- A stiff linkage and a corroded connector. The semi-active shock itself was sound. The dealer quote had proposed the unit
- Discussed in
- To Buy A Pre-Owned Bike
Front wheel speed intermittent
- Vehicle or context
- 2019 BMW S 1000 XR
- How it was handled
- A sensor face packed with corrosion. Air gap correct and toothed ring undamaged. The dealer quote had proposed the braking module
- Discussed in
- To Buy A Pre-Owned Bike
Recorded under-voltage events
- Vehicle or context
- 2019 BMW S 1000 XR
- How it was handled
- Events logged at cranking rather than while running, with charging output correct. A dead battery and a loose positive terminal, not the charging system
- Discussed in
- To Buy A Pre-Owned Bike
A machine that read perfectly and was not sound
- Vehicle or context
- 2018 BMW R 1200 GS Adventure
- How it was handled
- Zero faults on every module. The lift found a weeping final drive, both fork seals, corroded brake lines and eight-year-old tyres. About $2,900
- Discussed in
- To Buy A Pre-Owned Bike
A seized brake caliper piston
- Vehicle or context
- 2019 BMW S 1000 XR
- How it was handled
- Scope boundary. A firm lever proves hydraulics, not the caliper. Found on the lift, dragging on the drive from Los Angeles
- Discussed in
- To Buy A Pre-Owned Bike
An expensive interval service nobody would quote
- Vehicle or context
- 2015 Ducati Panigale 899
- How it was handled
- Valve clearances overdue and undocumented. Two shops declined to quote before opening the engine. Rejected as unquotable rather than expensive
- Discussed in
- To Buy A Pre-Owned Bike
No local support network
- Vehicle or context
- 2016 MV Agusta F3 800
- How it was handled
- Four phone calls established that parts were unpredictable and no shop would estimate a diagnosis. Rejected on serviceability rather than condition
- Discussed in
- To Buy A Pre-Owned Bike
Fuel trims drifting positive with altitude
- Vehicle or context
- Both vehicles
- How it was handled
- Expected. Air pressure falls about a third by 10,000 feet. The test is not whether a reading moved but whether it moved back, and it did
- Discussed in
- For The Road Trip
Transmission fluid temperature on a loaded grade
- Vehicle or context
- Honda Odyssey
- How it was handled
- Not in the standardized parameter set on that vehicle. Reached with the better adapter. A threshold agreed in advance and watched by a passenger
- Discussed in
- For The Road Trip
Coolant temperature under sustained load
- Vehicle or context
- Both vehicles
- How it was handled
- Rose and stabilised, which is a cooling system succeeding. Distinguished from a temperature that climbs and keeps climbing
- Discussed in
- For The Road Trip
Charging voltage as a control reading
- Vehicle or context
- Both vehicles
- How it was handled
- Flat all week regardless of altitude or heat. When several values move together and one holds, the movement is a shared condition
- Discussed in
- For The Road Trip
Tyre pressures moving daily
- Vehicle or context
- Both vehicles
- How it was handled
- About one psi per ten degrees Fahrenheit. All four moving together is weather
- Discussed in
- For The Road Trip
A screw in a front tyre
- Vehicle or context
- Honda Odyssey
- How it was handled
- One wheel reading below its neighbours across two dated readings four days apart. Repaired properly with a plug and patch
- Discussed in
- For The Road Trip
Charging dip under night accessory load
- Vehicle or context
- BMW S 1000 XR
- How it was handled
- Six accessories on a small alternator after dark. Recognised as a change only because a year of morning readings existed
- Discussed in
- For The Road Trip
Evaporative emissions fault after a fuel stop
- Vehicle or context
- Honda Odyssey
- How it was handled
- A fuel cap not clicked. Tightened, not cleared, and the lamp extinguished by the vehicle's own monitoring two days later
- Discussed in
- For The Road Trip
Sixty miles with no fuel available
- Vehicle or context
- BMW S 1000 XR
- How it was handled
- Range planned from the trip meter and a worst-case figure rather than from the gauge or the range estimate
- Discussed in
- For The Road Trip
Brake heat on a 3,000 foot descent
- Vehicle or context
- Both vehicles
- How it was handled
- Scope boundary. No sensor exists for pad, disc or fluid temperature. Managed with a lower gear and short firm applications
- Discussed in
- For The Road Trip
Self-tests incomplete at handover
- Vehicle or context
- Mexican-market compact crossover, rental
- How it was handled
- A battery fitted eleven days earlier. Established by asking once at the counter and written onto the condition form and initialled
- Discussed in
- On International Road Trip to Latin America
Fault appearing 41 minutes into a rental
- Vehicle or context
- Mexican-market compact crossover
- How it was handled
- Recorded conditions gave distance since the fault set. Against the handover odometer it placed the event after collection, not before, and the method reported that honestly
- Discussed in
- On International Road Trip to Latin America
A damage claim at drop-off
- Vehicle or context
- Mexican-market compact crossover
- How it was handled
- A wheel scrape defeated by six seconds of timestamped handover video. The scanner contributed nothing to this and the book says so
- Discussed in
- On International Road Trip to Latin America
A car that would not communicate at all
- Vehicle or context
- Costa Rican small four-wheel-drive
- How it was handled
- Neither adapter could establish a connection. Refused, and a different vehicle requested as a stated preference rather than an allegation
- Discussed in
- On International Road Trip to Latin America
Two stored faults with complete self-tests
- Vehicle or context
- Costa Rican small four-wheel-drive
- How it was handled
- Accepted in preference to a car with no faults and a wiped memory. An intact record is worth more than an empty one
- Discussed in
- On International Road Trip to Latin America
Wheel speed circuit fault after standing rain
- Vehicle or context
- Costa Rican small four-wheel-drive
- How it was handled
- Water bridging pins in a connector at 1,400 metres. Not cleared, not investigated, reported the same day, and it never returned
- Discussed in
- On International Road Trip to Latin America
An impact-damage claim at drop-off
- Vehicle or context
- Costa Rican small four-wheel-drive
- How it was handled
- The agent read the same fault with his own tool. Recorded conditions showed it set while stationary and cold after overnight rain, not by impact while driving
- Discussed in
- On International Road Trip to Latin America
Altitude on the Monteverde climb
- Vehicle or context
- Costa Rican small four-wheel-drive
- How it was handled
- Trims rose and returned. Charging voltage held, which made the rest interpretable
- Discussed in
- On International Road Trip to Latin America
Tyre pressures on a hot coast
- Vehicle or context
- Costa Rican small four-wheel-drive
- How it was handled
- The placard figure means cold. Adjusting after two hours of hot driving under-inflates a correct tyre
- Discussed in
- On International Road Trip to Latin America
Vibration on unpaved sections
- Vehicle or context
- Costa Rican small four-wheel-drive
- How it was handled
- A ninety second reading taken after every rough section, not only every morning
- Discussed in
- On International Road Trip to Latin America
Recently cleared memory at a consignment lot
- Vehicle or context
- 2016 camper van on a gasoline chassis
- How it was handled
- Fast tests complete, slow tests not ready. Resolved by a phone call to the servicing shop while standing there: a flat battery jump-started and replaced nine days earlier
- Discussed in
- To Buy A Used RV
A warm engine at a private viewing
- Vehicle or context
- Camper van, Elk Grove
- How it was handled
- Returned on a Saturday for a cold start. Misfire counters at zero, trims within a percent, coolant rising normally
- Discussed in
- To Buy A Used RV
Charging voltage under full house load
- Vehicle or context
- 2017 camper van
- How it was handled
- Dropped to 13.2 volts with the inverter and refrigerator running. A limitation rather than a fault, and costed as a first-year battery replacement
- Discussed in
- To Buy A Used RV
Everything a scanner cannot reach on a coach
- Vehicle or context
- All candidates
- How it was handled
- Scope boundary and the book's spine. A soft floor beside a wet bath, cracked roof sealant, a soft ceiling, a weight label, a converter that had ceased trading and a registration classification problem. None of it reports to any connector
- Discussed in
- To Buy A Used RV
Condition items found by a certified inspector
- Vehicle or context
- 2017 camper van
- How it was handled
- About $1,490 across brakes below the service limit, a seized water heater bypass valve, a refrigerator slow on propane, and expired alarms. Not one item appeared on any screen
- Discussed in
- To Buy A Used RV
A pending fault present at handover
- Vehicle or context
- Moto Guzzi V85 TT, rental
- How it was handled
- An oxygen sensor circuit. Photographed at handover, matched against the owner's own fleet reading from four days earlier, and written onto the file
- Discussed in
- For A Rented Bike Trip In Italy
That fault maturing mid-trip
- Vehicle or context
- Moto Guzzi V85 TT
- How it was handled
- Became a stored fault on day four. Three independent records already agreed on when it had first appeared, so the conversation was about facts rather than assertions
- Discussed in
- For A Rented Bike Trip In Italy
Charging voltage across six days of accessory load
- Vehicle or context
- Moto Guzzi V85 TT
- How it was handled
- Two phones, a camera and navigation. Flat at 14.2 to 14.3 volts every morning. Six identical readings are what would have made a seventh different one legible
- Discussed in
- For A Rented Bike Trip In Italy
Altitude on the climb to Gangi
- Vehicle or context
- Moto Guzzi V85 TT
- How it was handled
- Trims rose and returned across a thousand metres. Charging held, which made the rest interpretable
- Discussed in
- For A Rented Bike Trip In Italy
Whether the traveller's equipment would fit
- Vehicle or context
- Moto Guzzi V85 TT
- How it was handled
- European machines built to the recent emissions steps carry an industry standard connector, so a twenty dollar harness fitted without any model-specific hardware
- Discussed in
- For A Rented Bike Trip In Italy
Closing the rental cleanly
- Vehicle or context
- Moto Guzzi V85 TT
- How it was handled
- A final scan taken in the yard before the owner came out, and the stored fault raised by the renter first. Deposit of 900 euro released in full
- Discussed in
- For A Rented Bike Trip In Italy
The European harness did not fit
- Vehicle or context
- Thai-market 160cc automatic
- How it was handled
- A manufacturer four-pin connector rather than the European six-pin standard. A different harness bought in Bangkok for about a dollar, after a day and a half of establishing which one
- Discussed in
- For A Rented Gasoline Bike In Asia
A machine that would not communicate
- Vehicle or context
- Thai-market 160cc automatic, first offered
- How it was handled
- No connection on any protocol after nine minutes. Declined, and a different machine requested. It cost twenty minutes and nobody minded
- Discussed in
- For A Rented Gasoline Bike In Asia
Four stored faults with no explanation
- Vehicle or context
- Thai-market 160cc automatic, second offered
- How it was handled
- Faults accumulate on any machine nobody clears. Four unknowns declined in favour of two faults with an explanation each
- Discussed in
- For A Rented Gasoline Bike In Asia
Charging half a volt out of pattern
- Vehicle or context
- Thai-market 160cc automatic
- How it was handled
- Traced to a battery pack left in a live accessory socket overnight. The socket stays live with the key off and a small battery has almost no reserve
- Discussed in
- For A Rented Gasoline Bike In Asia
Ignition circuit fault after a downpour
- Vehicle or context
- Thai-market 160cc automatic
- How it was handled
- Water inside a connector. The screen said which circuit; a roadside mechanic with no equipment at all found and fixed it in twenty minutes. Photographed before and after and reported to the owner the same day
- Discussed in
- For A Rented Gasoline Bike In Asia
A breakdown with no mobile signal
- Vehicle or context
- A second 160cc automatic in the group
- How it was handled
- A fuel delivery circuit fault. It converted an unknown into a category, which turned a mechanical question into a transport question in about four minutes
- Discussed in
- For A Rented Gasoline Bike In Asia
Closing an informal rental
- Vehicle or context
- Thai-market 160cc automatic
- How it was handled
- No condition form, no deposit process and no fleet record existed. Every piece of evidence was the renter's own. Final scan taken and the repair raised first
- Discussed in
- For A Rented Gasoline Bike In Asia
Identification number credibility
- Vehicle or context
- Compact electric hatchback, rental
- How it was handled
- The number the car reported about itself checked against the rental agreement in thirty seconds
- Discussed in
- For A Rented Electric Car In Bali
Two stored faults at handover
- Vehicle or context
- Compact electric hatchback
- How it was handled
- Both from a parking incident in April. The owner produced the repair invoice on the spot, on the day of collection rather than in an email later
- Discussed in
- For A Rented Electric Car In Bali
The only useful diagnostic number
- Vehicle or context
- Compact electric hatchback
- How it was handled
- Pack voltage, recorded as a pair with the state of charge at the same moment, every morning. Worthless on its own and useful across nine mornings
- Discussed in
- For A Rented Electric Car In Bali
A voltage reading out of pattern
- Vehicle or context
- Compact electric hatchback
- How it was handled
- The one false alarm in ten books. Explained in ninety seconds by a state of charge four points lower after a power cut. The alarm working, and the answer being boring
- Discussed in
- For A Rented Electric Car In Bali
What a generic tool cannot reach on an EV
- Vehicle or context
- Compact electric hatchback
- How it was handled
- Scope boundary and the book's spine. Cell balance, state of health, battery and inverter temperatures, charging history and insulation resistance. All of it manufacturer-specific with no standard behind it
- Discussed in
- For A Rented Electric Car In Bali
Range that bore no relation to the brochure
- Vehicle or context
- Compact electric hatchback
- How it was handled
- Replaced with kilometres per percent, measured over one day in the actual conditions. No tool required
- Discussed in
- For A Rented Electric Car In Bali
Weaker regeneration after parking in the sun
- Vehicle or context
- Compact electric hatchback
- How it was handled
- A warm pack accepts charge more slowly. Not observable on that tool, and the correct response was to use the friction brakes rather than to investigate
- Discussed in
- For A Rented Electric Car In Bali
Brakes sounding wrong on a wet morning
- Vehicle or context
- Compact electric hatchback
- How it was handled
- Surface corrosion on discs barely used because the motor does the slowing. A few firm applications at low speed cleared it
- Discussed in
- For A Rented Electric Car In Bali
A cheap scooter reading better than a modern car
- Vehicle or context
- Thai-market 160cc automatic, hired in Bali
- How it was handled
- The comparison that closes the series. The tool was built for engines and emissions, and an electric car has neither
- Discussed in
- For A Rented Electric Car In Bali
Heavy-truck systems outside the scanner scope
- Vehicle or context
- Tractor and trailer combination
- How it was handled
- Tractor braking faults are visible. Trailer braking, trailer tyre pressure and refrigeration telemetry are not, because they ride on a separate communication path. Tyres, brake linings, king pin, fifth wheel, frame rails and rust are physical inspection items no scanner reads.
- Discussed in
- Buying a Used Truck
Distance and time since the last fault-code clear
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Concealment and history integrity
- Discussed in
- Buying a Used Truck
Inactive and historic fault log with per-fault occurrence counts
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Concealment and history integrity
- Discussed in
- Buying a Used Truck
Emissions monitor readiness, and why not ready on a just-serviced truck is a question
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Concealment and history integrity
- Discussed in
- Buying a Used Truck
Faults that cannot be erased by a clear command or a battery disconnect
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Concealment and history integrity
- Discussed in
- Buying a Used Truck
ECM identification and serial cross-checked against title, history report and door jamb
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Concealment and history integrity
- Discussed in
- Buying a Used Truck
Total ECM engine hours against odometer miles
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- True duty cycle, as distinct from odometer
- Discussed in
- Buying a Used Truck
Lifetime idle hours and idle percentage
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- True duty cycle, as distinct from odometer
- Discussed in
- Buying a Used Truck
Power take-off hours, revealing non-highway work the listing did not mention
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- True duty cycle, as distinct from odometer
- Discussed in
- Buying a Used Truck
Lifetime fuel burned against lifetime miles, producing a real historical economy figure
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- True duty cycle, as distinct from odometer
- Discussed in
- Buying a Used Truck
Stored parameters such as maximum road speed and idle shutdown, fingerprinting the prior fleet
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- True duty cycle, as distinct from odometer
- Discussed in
- Buying a Used Truck
Diesel particulate filter soot load
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Aftertreatment
- Discussed in
- Buying a Used Truck
Diesel particulate filter ash load, and why ash is the number that costs money
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Aftertreatment
- Discussed in
- Buying a Used Truck
Filter differential pressure at a known engine speed
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Aftertreatment
- Discussed in
- Buying a Used Truck
Regeneration history: successful count, interval trend, aborted and incomplete events
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Aftertreatment
- Discussed in
- Buying a Used Truck
Distance and time since the last completed parked regeneration
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Aftertreatment
- Discussed in
- Buying a Used Truck
Selective catalytic reduction conversion efficiency from upstream and downstream readings
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Aftertreatment
- Discussed in
- Buying a Used Truck
Exhaust fluid consumption against fuel consumption, as a dosing plausibility check
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Aftertreatment
- Discussed in
- Buying a Used Truck
Exhaust fluid quality, level sensor and tank heater circuit fault history
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Aftertreatment
- Discussed in
- Buying a Used Truck
Cylinder contribution test, stationary and only with written seller consent
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Engine mechanical
- Discussed in
- Buying a Used Truck
Fuel rail pressure, commanded against actual, at idle and under load
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Engine mechanical
- Discussed in
- Buying a Used Truck
Crankcase pressure as a blowby indicator where broadcast
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Engine mechanical
- Discussed in
- Buying a Used Truck
Oil pressure across the speed range at full operating temperature
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Engine mechanical
- Discussed in
- Buying a Used Truck
Coolant behaviour and fan on-percentage, exposing a tired cooling package
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Engine mechanical
- Discussed in
- Buying a Used Truck
Turbocharger vane position, commanded against actual, and what sticking looks like
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Air handling, drivetrain, brakes
- Discussed in
- Buying a Used Truck
Boost pressure and intake manifold temperature on a sustained grade
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Air handling, drivetrain, brakes
- Discussed in
- Buying a Used Truck
Automated transmission clutch remaining life and shift actuator fault history
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Air handling, drivetrain, brakes
- Discussed in
- Buying a Used Truck
Transmission fluid temperature under a loaded climb
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Air handling, drivetrain, brakes
- Discussed in
- Buying a Used Truck
Air governor cut-in and cut-out, tank build time and compressor duty cycle
- Vehicle or context
- Class 8 heavy truck
- What the book checks
- Air handling, drivetrain, brakes
- Discussed in
- Buying a Used Truck
Erratic sensor circuit (SPN/FMI pair): Intermittent derate in the field since previous autumn; fault traced to a corroded harness connector, not a failed sensor
- Vehicle or context
- Agricultural (tractor, HD-OBD/J1939)
- How it was handled
- Cleaned and resealed connector, rerouted harness clear of chafe point; confirmed via re-read
- Discussed in
- To Fix Your Current Tractor
High soot load (no fault code): Exhaust filter soot accumulating because winter loader work never reaches passive-regeneration temperature
- Vehicle or context
- Agricultural (tractor)
- How it was handled
- Ran a parked regeneration outdoors on bare ground; raised engine speed for light loader work; completed parked cycles promptly instead of shutting off
- Discussed in
- To Fix Your Current Tractor
Rising ash load (no fault code): Ash accumulation is permanent and only ever increases; four data points extended forward to forecast filter-service date
- Vehicle or context
- Agricultural (tractor)
- How it was handled
- No fix possible (ash cannot be removed except by service); tracked oil consumption and regeneration frequency as levers; budgeted for future filter service
- Discussed in
- To Fix Your Current Tractor
Rail pressure gap (commanded vs actual, diverging under load): Fuel system restriction — contaminated primary/secondary filters from bulk farm diesel tank
- Vehicle or context
- Agricultural (tractor)
- How it was handled
- Replaced primary and secondary fuel filters; cut open old filter to confirm contamination; began draining water from bulk tank periodically
- Discussed in
- To Fix Your Current Tractor
High idle-hour share: 28% of engine life spent idling, found via ECU's idle-hours register rather than the dashboard hour meter
- Vehicle or context
- Agricultural (tractor)
- How it was handled
- Behavioural changes: stopped idling during gate work, shut off at the elevator, shortened warm-up time
- Discussed in
- To Fix Your Current Tractor
Fan duty vs coolant temperature mismatch: Cooling system working at capacity (fan at full for 6 of 12 minutes) due to chaff-packed cooling stack
- Vehicle or context
- Agricultural (tractor)
- How it was handled
- Cleaned cooling stack from the back forward, engine off, air line, eye protection
- Discussed in
- To Fix Your Current Tractor
Fluid quality sensor fault (harvest, derate countdown): Derate countdown triggered mid-harvest; fault named the fluid quality sensor but traced to a corroded/chafed harness connector at the tank
- Vehicle or context
- Agricultural (tractor)
- How it was handled
- Mechanic cleaned connector, replaced seal, rerouted harness clear of chafe line, cleared fault after repair
- Discussed in
- To Fix Your Current Tractor
Hour meter mismatch (display vs ECU register): Display showed 4,820 hrs; ECU register showed 11,460 hrs — corroborated by lifetime fuel, load-factor history, regen count and physical wear
- Vehicle or context
- Agricultural (used tractor, pre-purchase)
- How it was handled
- No repair — used as a disqualifying finding; buyer walked away from purchase
- Discussed in
- To Buy A Used Tractor
Fault memory cleared (6.4 hrs prior): Entire fault history erased ~6 hours before buyer's inspection at a dealer lot; no corroborating work order produced
- Vehicle or context
- Agricultural (used tractor)
- How it was handled
- No repair — buyer requested work order, none produced; declined purchase; offered to return once monitors/faults re-accumulated
- Discussed in
- To Buy A Used Tractor
Ash load high under falsely low soot (post-regen deception): 84% ash loading masked by a parked regeneration run the morning of the sale, producing a misleadingly low soot reading
- Vehicle or context
- Agricultural (used tractor)
- How it was handled
- No repair — priced the known filter-service cost into a maximum bid rather than rejecting outright; lost at auction above ceiling
- Discussed in
- To Buy A Used Tractor
Advertised duty cycle vs load-factor history mismatch: Seller's ad claimed "light chores," but ECU load-factor and PTO-hour history showed sustained heavy-duty use
- Vehicle or context
- Agricultural (used tractor)
- How it was handled
- No repair — used as disqualifying finding (use history could not be established); buyer declined purchase
- Discussed in
- To Buy A Used Tractor
Weak cylinder(s) + crankcase blow-by: Cylinder cutout/contribution test showed two cylinders contributing ~1/3 of normal; confirmed with visible blow-by at oil filler
- Vehicle or context
- Agricultural (used tractor)
- How it was handled
- No repair — pointed to compression (engine-out) rather than injector fault; buyer declined purchase
- Discussed in
- To Buy A Used Tractor
Transmission over-temperature events (clustered): 31 over-temperature events and 88 clutch-slip events clustered in a 250-hour window years earlier, undetectable via engine data alone
- Vehicle or context
- Agricultural (used tractor)
- How it was handled
- No repair — confirmed live via a loaded demonstration showing temperature still climbing after 25 minutes; buyer declined purchase
- Discussed in
- To Buy A Used Tractor
Erratic electrical fault (occurrence count 40+, load/vibration only): Intermittent circuit fault a dealership could not reproduce in 9 days of shop time; freeze frames showed it only occurred under load and vibration
- Vehicle or context
- Agricultural (used tractor)
- How it was handled
- Diagnosed and repaired: chafed harness section behind the step, repaired for $240 including call-out; bought at auction below ceiling
- Discussed in
- To Buy A Used Tractor
P0442: Small evaporative (EVAP) system leak; six weeks of an intermittent lamp caused by a hardened/split filler-cap seal
- Vehicle or context
- Passenger car (2016 Honda Pilot, petrol)
- How it was handled
- Replaced filler cap (~$22); did not clear the code — let the vehicle's own monitor confirm the repair and extinguish the lamp itself
- Discussed in
- To Fix Your Own Car In Canada
Misfire, cylinder 5 (214 occurrences): Single-cylinder misfire flagged via misfire counters; located via a coil-swap test (swap suspect coil to another cylinder, clear counts, re-drive, re-read)
- Vehicle or context
- Passenger car
- How it was handled
- Replaced ignition coil and spark plugs (~$310) after coil-swap test confirmed the fault followed the coil
- Discussed in
- To Fix Your Own Car In Canada
Declining cranking voltage (no code, trend only): Cranking voltage tracked monthly fell from 10.4V to 9.0V over ten weeks with no warning lamp at any point
- Vehicle or context
- Passenger car
- How it was handled
- Replaced battery proactively before failure, at a chosen time and shop, once voltage crossed a pre-set 9.6V action threshold (~$240)
- Discussed in
- To Fix Your Own Car In Canada
Slow tyre pressure decline (no code, trend only): Cold tyre pressure tracked monthly showed one tyre losing ~5–6 kPa/day while three held steady
- Vehicle or context
- Passenger car
- How it was handled
- Found and repaired a self-sealing roofing-nail puncture via plug-and-patch from inside (~$35)
- Discussed in
- To Fix Your Own Car In Canada
Intermittent cold-weather code (second vehicle, unresolved): Code on a 2011 Toyota Sienna appearing only below approx. −15°C and self-clearing when warm
- Vehicle or context
- Passenger car (van)
- How it was handled
- Not resolved in the book — logged for a future garage visit; used as an example of documenting an intermittent fault rather than guessing
- Discussed in
- To Fix Your Own Car In Canada
Incomplete readiness monitors (rejection, not a fault code): Vehicle rejected at California Smog Check after owner disconnected the battery to clear a lamp, resetting all readiness monitors to "incomplete"
- Vehicle or context
- Passenger car (2012 Honda CR-V)
- How it was handled
- No repair needed for the reset itself — completed a deliberate ~140-mile drive cycle (cold start, city driving, sustained highway, coast-down) to re-complete the monitors
- Discussed in
- Katie's Smog Test Jitters
P0442: Small EVAP leak, confirmed via freeze frame (parked, warm, tank ~46% full — matching EVAP self-test conditions)
- Vehicle or context
- Passenger car
- How it was handled
- Replaced filler cap (~$22); did not clear the code, let the readiness monitor confirm the repair
- Discussed in
- Katie's Smog Test Jitters
Pending code (no lamp): A second, unrelated pending fault found on the same vehicle that never triggered the dashboard lamp and disappeared within a week
- Vehicle or context
- Passenger car
- How it was handled
- No repair — logged with a date as an early-warning record; no action needed since it did not recur
- Discussed in
- Katie's Smog Test Jitters
P0420: Catalyst efficiency below threshold; a shop quoted a full catalytic converter (~$1,840) based on the code alone
- Vehicle or context
- Passenger car (colleague's vehicle)
- How it was handled
- Diagnosis corrected using fuel trims and downstream O2 sensor behaviour: actual cause was an exhaust gasket leak before the downstream sensor, repaired for ~$68
- Discussed in
- Katie's Smog Test Jitters
Incomplete monitors on a hybrid (no fault): Hybrid engine cycling on/off in city driving repeatedly interrupted self-tests, especially the catalyst monitor
- Vehicle or context
- Passenger car (2018 Toyota RAV4 Hybrid)
- How it was handled
- No repair — completed via a sustained highway drive (a weekend trip) that kept the engine running continuously long enough to finish the monitors
- Discussed in
- Katie's Smog Test Jitters
Cleared code before test (rejection): Neighbour cleared a code with a reader the morning of his own test; caused an immediate rejection for unmet readiness rather than the original fault being addressed
- Vehicle or context
- Passenger car (neighbour's vehicle)
- How it was handled
- No fix from clearing — vehicle later diagnosed properly (sensor fault), sensor replaced, and passed on a rescheduled test with the readiness monitors legitimately re-completed
- Discussed in
- Katie's Smog Test Jitters
Positive long-term fuel trim (misdiagnosed): Fuel trim of +11% at idle and a slight hesitation were initially and incorrectly attributed to a "lazy" oxygen sensor
- Vehicle or context
- Passenger car
- How it was handled
- Correct cause found by a mechanic: a loose air-intake clamp downstream of the airflow sensor, tightened at no cost; sensor was healthy
- Discussed in
- Katie's Smog Test Jitters
P0401 (EGR insufficient flow, 14 occurrences): Recirculation valve intermittently restricted by wet-carbon buildup from short urban journeys; confirmed via commanded-vs-actual valve position lag under load
- Vehicle or context
- Passenger car — diesel (2013 Ford Focus 1.6 TDCi)
- How it was handled
- Valve removed, cleaned, passage cleared and refitted at an independent garage (~£140)
- Discussed in
- To Fix An Old Car In England
P0670-type (glow plug control circuit, 6 occurrences): Fault only occurred below ~5°C intake air temperature (found via freeze-frame plotting), which is why it never reproduced during a warm workshop visit
- Vehicle or context
- Passenger car — diesel
- How it was handled
- Circuit tested cold and two of four plugs replaced (~£210); explained that glow plugs also assist regeneration, not just starting
- Discussed in
- To Fix An Old Car In England
High soot loading (no fault code, live PID): DPF soot loading at 78% on a car doing almost exclusively 4-mile school-run journeys, never reaching regeneration temperature
- Vehicle or context
- Passenger car — diesel
- How it was handled
- Deliberate 40-minute sustained-speed motorway drive (A11) to trigger and complete a regeneration; adopted a fortnightly longer-journey habit afterward
- Discussed in
- To Fix An Old Car In England
Underboost fault (turbo pressure code): Requested-vs-actual boost pressure diverged under load; a garage quoted a full turbocharger (£1,180) from the code alone
- Vehicle or context
- Passenger car — diesel
- How it was handled
- Diagnosis corrected using the commanded-vs-actual boost trace and a 2-year-old MOT advisory about a minor exhaust leak: found a split boost hose, repaired for £34 (parts) + £55 labour
- Discussed in
- To Fix An Old Car In England
Cold-running engine (no fault code): Coolant never reaching normal operating temperature (peaking ~62°C instead of ~88°C); found only by comparing monthly logged readings against a neighbour's car
- Vehicle or context
- Passenger car — diesel
- How it was handled
- Diagnosed as a thermostat stuck open; replaced thermostat and housing (~£89), which also improved fuel economy and soot loading
- Discussed in
- To Fix An Old Car In England
ABS lamp / wheel-speed sensor fault: Anti-lock braking lamp on; a generic OBD2 app read no codes at all because ABS data is outside the standardised emissions PID set
- Vehicle or context
- Passenger car
- How it was handled
- Read via a marque-specific app; found corrosion at the nearside-rear wheel-speed sensor connector; cleaned and resealed (~£40)
- Discussed in
- To Fix An Old Car In England
Airbag (SRS) lamp / seat connector: Airbag lamp illuminated after an interior valet disturbed a connector under the seat (colleague's car)
- Vehicle or context
- Passenger car
- How it was handled
- Connector reseated (~4 minutes); explicit caution given that airbag systems are pyrotechnic and not for casual DIY disassembly
- Discussed in
- To Fix An Old Car In England
AdBlue/SCR dosing fault (mileage countdown): Dashboard showed a distance-to-no-restart countdown; owner mistakenly topped up AdBlue fluid rather than addressing the dosing module fault
- Vehicle or context
- Passenger car — newer diesel (2019 estate)
- How it was handled
- Diagnosed as a dosing module fault (not a fluid level issue) via the scanner; repaired at a franchised dealer (£600+)
- Discussed in
- To Fix An Old Car In England
Security gateway limiting generic tool access: A newer vehicle restricted a generic OBD2 tool to reading only; module clearing/writing was blocked without manufacturer authentication
- Vehicle or context
- Passenger car — newer diesel
- How it was handled
- No repair needed — reading (codes, freeze frames, live data, dosing figures) remained possible; noted as a limitation rather than a fault to fix
- Discussed in
- To Fix An Old Car In England
Security-gateway restricted read (pre-purchase): Newer car's gateway blocked a generic scanner from reading braking, airbag, transmission and service-counter modules; only standard engine/emissions data was reachable
- Vehicle or context
- Passenger car — used purchase (2019 VW Golf)
- How it was handled
- No repair — buyer asked seller to fund an independent inspection with proper equipment and to produce their own recent diagnostic report; did not purchase on unrelated budget grounds
- Discussed in
- To Buy A Used Car In England
Fault memory cleared 12 miles prior (pre-purchase): High-mileage car showed zero stored faults and four incomplete readiness self-checks, with the memory cleared only 12 miles before viewing — consistent with the prep workshop's distance from the forecourt
- Vehicle or context
- Passenger car — used purchase (2017 Ford Focus)
- How it was handled
- No repair — buyer requested the workshop job sheet naming the fault; none was produced; declined purchase
- Discussed in
- To Buy A Used Car In England
Ash loading 91% under a 7% soot reading (pre-purchase): Diesel particulate filter effectively at end-of-life (ash), masked by a low soot reading because the seller had driven the car just before the viewing, completing a regeneration
- Vehicle or context
- Passenger car — used purchase, diesel (2016 Vauxhall Astra)
- How it was handled
- No repair — cross-checked with regeneration-cycle history (7 cycles in the last 200 miles vs a lifetime average of 1 in 138); buyer declined at asking price
- Discussed in
- To Buy A Used Car In England
Service/wear counters contradicting the advert (pre-purchase): "Full service history / just serviced / brakes done last year" claims contradicted by the car's own oil-service, brake-pad-life and brake-fluid counters
- Vehicle or context
- Passenger car — used purchase (2018 BMW 320d)
- How it was handled
- No repair — buyer offered a reduced price reflecting the discrepancy; seller declined and relisted with the false claim removed
- Discussed in
- To Buy A Used Car In England
Fault memory cleared 3 miles prior + inaccessible airbag module (pre-purchase): Seller's ad showed a dashboard photo with no warning lights; scan (before seller withdrew permission) showed the memory had been cleared 3 miles earlier and 5 readiness checks were incomplete
- Vehicle or context
- Passenger car — used purchase (2017 Nissan Qashqai)
- How it was handled
- No repair — seller withdrew permission mid-scan; buyer stopped immediately and walked away, treating the refusal as an unresolved data point rather than accusing the seller
- Discussed in
- To Buy A Used Car In England
Glow-plug circuit fault, 27 occurrences, dismissed as "just the cold" (pre-purchase): Seller/salesman described a stored glow-plug fault as normal cold-weather behaviour; freeze-frame plotting showed all 27 occurrences below 8°C, indicating a real intermittent fault rather than a characteristic
- Vehicle or context
- Passenger car — used purchase, diesel (2016 Peugeot 308)
- How it was handled
- No repair — buyer priced a glow-plug replacement (£240–£380) and a related elevated ash reading into a reduced offer; seller declined
- Discussed in
- To Buy A Used Car In England
Ash loading 74% + rear suspension corrosion (pre-purchase, honest seller): Ten-year-old car with a complete, genuine service history still carried a near-end-of-life particulate filter and early rear-suspension corrosion, both invisible to the seller
- Vehicle or context
- Passenger car — used purchase, diesel (2015 Honda Civic)
- How it was handled
- No repair — buyer disclosed both findings to the seller, offered a reduced price reflecting quoted repair costs; seller declined, later confirmed findings independently and relisted with the issues disclosed
- Discussed in
- To Buy A Used Car In England
Airbag circuit fault, 31 occurrences (pre-purchase; purchased car): Disclosed "known airbag fault" at auction had deterred other bidders after a dealer quoted ~£940 for an open-ended investigation; scanner data (cleared-memory distance, occurrence count, other systems clean) suggested a lower-risk cause
- Vehicle or context
- Passenger car — used purchase (2017 Skoda Octavia estate)
- How it was handled
- Purchased at auction below ceiling bid; found and repaired: a disturbed connector under the driver's seat, professionally reconnected and cleared (~£45), versus the ~£940 worst-case priced into the bid
- Discussed in
- To Buy A Used Car In England
Recurring lessons
Frequently asked through the series
These are repeated diagnostic patterns, not part-replacement instructions.
A recently cleared memory, shown by fast self-tests complete and slow ones not ready
This pattern appears in: Car, pre-owned motorcycle, RV, Baja rental, truck.
A fault dated to before or after a handover using recorded conditions
This pattern appears in: Baja rental, Costa Rica rental, Italy rental.
Charging voltage as the control reading that makes everything else interpretable
This pattern appears in: Every book without exception.
A reading out of pattern rather than out of range
This pattern appears in: Road trip, Costa Rica, RV, Thailand, Bali.
A warm engine concealing cold-start behaviour
This pattern appears in: Pre-owned motorcycle, RV.
Water bridging pins in a connector after heavy rain
This pattern appears in: Ninja 400, Costa Rica rental, Thailand scooter.
Altitude moving fuel trims, and them returning
This pattern appears in: Road trip, Costa Rica, Italy.
Tyre pressure following temperature at about one psi per ten degrees
This pattern appears in: Road trip, Costa Rica, Thailand.
A machine that will not communicate at all, treated as a finding
This pattern appears in: Costa Rica rental, Thailand scooter.
Coverage integrity
Where the register is summary-only
Maintaining a Used Truck
The record reachable from this conversation states that the book covers twenty six maintenance and operational problems caught proactively through a monthly nine minute diagnostic habit, across seventeen chapters. The itemised list of those twenty six is not reachable from here, and this register does not invent it. Its stated editorial thesis is reproduced because it is the argument the whole series rests on: the habit of regular proactive measurement is more valuable than reactive diagnostic capability, and no amount of capable real-time help substitutes for a historical record that was never created.
The original Sarah book
The record reachable from this conversation confirms the book exists and that it established the scope-boundary principle carried through every later title, but it does not contain the itemised issue list. That list is not reproduced here rather than being reconstructed from memory.