Look up any check-engine, ABS, or body-control code. Plain-English explanation, common causes, how a tech diagnoses it, and typical repair cost.
243 codes • full explainers generated on first visit
VVT solenoid or wiring fault on bank 1.
Cam timing too advanced — often low oil or stuck VVT.
Exhaust cam timing fault — VVT solenoid or oil flow.
Cam and crank out of sync — timing chain stretch is common.
Cam and crank out of sync, exhaust cam.
VVT solenoid or wiring fault on bank 2.
Upstream O2 sensor heater fault.
Downstream O2 sensor heater fault.
Fuel pressure out of spec — common on diesels.
MAF readings out of range — clean or replace sensor.
MAF signal too low — wiring or dirty sensor.
Intake air temp sensor reads too hot.
Coolant temp sensor or wiring shorted low.
Coolant temp sensor open circuit.
Engine not warming up — stuck-open thermostat.
Upstream O2 sensor lean — exhaust leak or fuel issue.
Aging O2 sensor switching too slowly.
Upstream O2 sensor heater failed.
Downstream O2 sensor low — often catalyst-related.
Downstream O2 heater fault.
Bank 2 upstream O2 lean.
Bank 2 upstream O2 heater fault.
Vacuum leak, dirty MAF, weak fuel pump.
Leaking injector, MAF, or fuel pressure regulator.
Vacuum leak or weak fuel delivery on bank 2.
Bank 2 running rich — injector or sensor.
Common on diesel — sensor or wiring fault.
Open injector circuit — wiring or coil.
Cylinder 1 injector electrical fault.
Engine overheated — stop driving.
ATF too hot — common when towing.
Boost leak, wastegate, or failing turbo.
Plugs, coils, fuel, or compression problem.
Misfire on cylinder 1 — coil, plug, or injector.
Misfire on cylinder 2.
Misfire on cylinder 3.
Misfire on cylinder 4.
Misfire on cylinder 5.
Misfire on cylinder 6.
Misfire on cylinder 7.
Misfire on cylinder 8.
Cold-start misfire — common on Ford modular V8s.
Knock sensor or wiring fault.
Crank sensor failed — no/intermittent start.
Cam sensor fault — rough run or no start.
Bank 2 cam sensor fault.
Coil-on-plug or wiring failure cylinder 1.
Carboned-up EGR valve or DPFE sensor.
EGR valve stuck open.
Common on Audi/VW — pump or check valve.
Air pump or piping leak.
Failing catalytic converter — verify with O2 readings.
Bank 2 catalyst worn or O2 sensor lying.
Loose gas cap, leaking line, or purge valve.
Often a loose or worn fuel cap.
Vent solenoid stuck — spider nest on Toyotas.
Big EVAP leak — start with the gas cap.
Tiny EVAP leak — needs smoke test.
Tighten or replace the fuel cap.
Sending unit in fuel tank failing.
Radiator fan or relay fault.
VSS failed — speedo, cruise, and ABS can be affected.
Throttle body or IAC issue.
Vacuum leak or throttle body sticking.
Sensor or wiring fault — verify actual oil pressure.
Stop driving — verify pressure with mechanical gauge.
Overcharging alternator.
Internal PCM failure — often needs reflash or replacement.
TCM has a stored code — scan transmission.
Trans input speed sensor failed.
Trans output speed sensor failed.
Slipping clutches or sensor — transmission service needed.
TCC solenoid or worn converter.
Internal trans solenoid fault.
Internal trans solenoid fault.
Common on GM 6L80/6L90 — valve body wear.
Common on Ford EcoBoost — turbo or MAF.
Clogged DPF — needs regen or service.
IMRC actuator failure.
Often a small exhaust leak after the cat.
Failed downstream O2 or cat.
Accelerator pedal sensor — reduced power.
APP sensor mismatch — limp mode.
Vacuum leak — often PCV or intake gasket.
Upstream O2 sensor failed.
Downstream O2 sensor failed.
Boost or vacuum leak.
DPF needs forced regen.
Timing chain stretch or VVT phaser fault, bank 1.
Timing chain stretch or VVT phaser fault, bank 2.
Intake cam stuck retarded — VVT solenoid or oil flow.
Exhaust VVT solenoid electrical fault, bank 1.
Exhaust cam stuck retarded, bank 1.
Bank 2 intake cam/crank out of sync.
Bank 2 exhaust cam/crank out of sync.
Bank 2 intake cam advanced — VVT phaser or oil.
Bank 2 exhaust cam over-advanced.
O2 heater wiring shorted low, B1S1.
O2 heater wiring shorted high, B1S1.
Downstream O2 heater shorted low.
Downstream O2 heater shorted high.
Bank 2 upstream O2 heater fault.
Airflow doesn't match throttle — vacuum leak or sensor.
Weak HPFP, clogged filter, or leaking injectors — common on diesels.
Sticking pressure regulator or HPFP overpressure.
FPR solenoid or wiring fault — common on diesels.
Post-intercooler IAT sensor fault on boosted engines.
Post-intercooler IAT reading implausible.
MAF wiring or sensor open/short.
MAF signal too high — sensor or wiring fault.
Manifold pressure reading implausible.
MAP signal shorted low.
MAP signal shorted high or unplugged.
Intake air temp reads implausibly cold.
Coolant temp doesn't track engine warm-up correctly.
Throttle/pedal sensor reading implausible.
Throttle position signal low.
Throttle position signal high.
Engine never reaches operating temp — thermostat stuck open.
Upstream O2 sensor general fault.
Upstream O2 stuck rich — sensor or wiring.
Dead upstream O2 sensor.
Downstream O2 sensor general fault.
Downstream O2 stuck rich — failing cat or sensor.
Dead downstream O2 sensor.
Aging bank 2 upstream O2 sensor.
Bank 2 downstream O2 low.
Bank 2 downstream O2 heater fault.
Bank 2 fuel trim out of range.
Rail pressure sensor reading implausible.
Diesel/GDI rail sensor shorted low.
Diesel/GDI rail sensor shorted high.
Cylinder 2 injector electrical fault.
Cylinder 3 injector electrical fault.
Cylinder 4 injector electrical fault.
Cylinder 5 injector electrical fault.
Cylinder 6 injector electrical fault.
Cylinder 7 injector electrical fault.
Cylinder 8 injector electrical fault.
RPM exceeded redline — money shift or trans fault.
Wastegate stuck or boost control fault.
Boost pressure sensor shorted high.
Underboost from leak, wastegate, or failing turbo.
V10 cyl 9 misfire — coil, plug, injector.
V10 cyl 10 misfire.
Needs a CASE relearn after CKP/PCM service.
RPM signal lost — usually crank sensor.
Knock sensor reading out of expected range.
Bank 2 knock sensor fault.
Cam sensor signal implausible.
Coil-on-plug fault cylinder 2.
Coil-on-plug fault cylinder 3.
Coil-on-plug fault cylinder 4.
Coil-on-plug fault cylinder 5.
Coil-on-plug fault cylinder 6.
Coil-on-plug fault cylinder 7.
Coil-on-plug fault cylinder 8.
EGR position sensor shorted low.
EGR position sensor shorted high.
Air pump or check valve fault.
AIR solenoid B electrical fault.
AIR pump relay control circuit.
Pre-cat efficiency low, bank 1.
Purge valve stuck or hose leak.
Purge solenoid electrical fault.
Vent solenoid electrical fault.
FTP sensor reading implausible.
FTP sensor shorted low.
FTP sensor shorted high or unplugged.
Purge valve leaking when commanded closed.
Purge flow lower than expected.
VSS reading implausible vs other sensors.
IAC valve or throttle body issue.
Sensor electrical fault — confirm with mechanical gauge.
Sensor or low oil pressure — verify.
Sensor shorted high or unplugged.
Charging system undervoltage.
Brake pedal switch fault — affects cruise, shift interlock.
Internal PCM memory error — reflash or replace.
KAM lost — usually low battery during start.
Internal PCM fault.
5V reference circuit fault — multiple sensors affected.
Trans input speed signal lost.
Trans output speed signal lost.
1st gear slip — solenoid or clutch pack.
2nd gear slip — solenoid or clutch pack.
3rd gear slip — solenoid or clutch pack.
4th gear slip — solenoid or clutch pack.
5th gear slip — solenoid or clutch pack.
TCC solenoid electrical fault.
TCC solenoid short/open.
Line pressure solenoid sticking — valve body wear.
Shift solenoid A mechanically stuck.
Shift solenoid B mechanically stuck.
Internal trans pressure solenoid B stuck.
Major internal trans slip — rebuild likely.
Drive cycle needed — common after battery disconnect.
IMRC position sensor fault.
Bank 2 post-cat lean — exhaust leak or sensor.
Bank 2 post-cat rich — failed downstream O2 or cat.
Drive-by-wire throttle motor fault.
TPS dual-track mismatch — limp mode.
Bypass/diverter valve stuck or torn diaphragm.
Diesel HEUI/HPFP overpressure — common on Ford 6.0L.
Pedal sensors disagree — reduced power.
AIR switching valve mechanical fault.
DPF regenerating too often — upstream issue.
PCM losing power momentarily — wiring/relay.
DPF dP sensor reading low — sensor or hose.
DPF restricted — needs regen or cleaning.
VGT/VNT actuator position sensor fault.
AFM/DFM lifter or solenoid fault — common GM V8.
AFM/DFM lifter or solenoid fault — common GM V8.
CAN bus or PCM power/ground problem.
Transmission module not responding.
ABS module offline — usually wiring/power.
BCM offline — accessories drop out.
IPC offline — dead gauges.
PCM sending bad data — reflash or replace.
CAN-A bus offline — wiring or module short.
FPCM offline — pump or wiring fault.
Hybrid/EV drive motor module offline.
Airbag (RCM/SDM) module offline.
Climate module offline.
Infotainment head unit offline.
SCCM offline — multifunction switches dead.
Module software mismatch — needs reflash.
Low system voltage — check battery and charging.
Body module needs programming after replacement.
Generic body module internal fault.
BCM-monitored brake switch fault.
Hybrid/EV pack voltage out of expected range.
Automatic headlight sensor fault.
Airbag circuit fault — service immediately.
ABS wheel speed sensor or wiring.
ABS wheel speed sensor or wiring.
Traction control or ABS disabled by another fault.
ABS wheel speed sensor or wiring.
ABS wheel speed sensor or wiring.
ABS pump motor fault.
ABS module relay fault.
Steering angle sensor needs calibration.
ABS sees engine code — fix engine first.