OBD-II Trouble Codes: Meaning & Fixes

C0035 Chassis The ABS module lost a valid signal from the driver-side front wheel speed sensor. Moderate P0135 Powertrain The heater inside the upstream oxygen sensor on bank 1 isn't working or its circuit is faulty. Low P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate B0001 Body The airbag module found a fault in the firing circuit for the driver's front airbag (stage 1). High P0113 Powertrain The intake air temperature signal is stuck at maximum voltage, which usually means an open… Low P0171 Powertrain The engine computer is adding the maximum extra fuel it's allowed on bank 1 and still sees… Moderate

P0236 Powertrain The boost sensor's signal is electrically OK, but its readings don't make sense compared… Moderate P0237 Powertrain The boost sensor signal has dropped near zero volts, reading less pressure than the atmosphere… Moderate P0238 Powertrain The boost sensor signal is stuck near 5 volts, so the computer sees impossibly high boost… Moderate P0243 Powertrain The engine computer found a fault in the electrical circuit of the solenoid that controls… Moderate P0263 Powertrain Cylinder 1 is producing noticeably more or less power than the others, beyond what fuel trim… Moderate P0266 Powertrain The engine computer can't even out cylinder 2 with fuel corrections; its balance rate is past… Moderate P0269 Powertrain Cylinder 3 isn't pulling its weight, or is pulling too hard, and the fuel correction for it… Moderate P0272 Powertrain The ECU can't balance cylinder 4 against the rest anymore; its fuel correction is outside… Moderate P0275 Powertrain The fuel correction for cylinder 5 is past its limit. Only engines with five or more cylinders… Moderate P0299 Powertrain The turbo or supercharger isn't building the boost pressure the engine computer is asking for. Moderate P0300 Powertrain The engine computer sees misfires that jump between cylinders or hit several cylinders at once. High P0301 Powertrain Cylinder 1 is repeatedly failing to fire. The cause is almost always its coil, plug, injector… Moderate P0302 Powertrain Cylinder 2 keeps misfiring. On inline engines it's a middle cylinder, so rule out coolant… Moderate P0303 Powertrain Cylinder 3 is misfiring. Check whether it misses at idle or under load before you blame… Moderate P0304 Powertrain Cylinder 4 is misfiring. Its end or rear position makes water, oil and intake leaks common… Moderate P0305 Powertrain Cylinder 5 is misfiring. First job: work out which bank it sits on, because that decides what… Moderate P0306 Powertrain Cylinder 6 is misfiring. On an inline-six it's the hot rear cylinder; on GM and Hemi V8s it can… Moderate P0307 Powertrain Cylinder 7 is misfiring. On GM and Hemi V8s it's a cylinder-deactivation cylinder, so check… Moderate P0308 Powertrain Cylinder 8 is misfiring. It's a rear V8 cylinder against the firewall, so its plug is often… Moderate P0320 Powertrain The computer lost the engine speed (rpm) signal. The engine can stall suddenly or refuse… High P0321 Powertrain The rpm signal is there but erratic: extra or missing pulses the computer can't trust. Expect… Moderate P0335 Powertrain The engine computer lost the crankshaft position signal. Expect stalling or a crank-no-start. High P0336 Powertrain Crank signal present but implausible: damaged teeth, a slipped balancer ring or debris confuse… Moderate P0337 Powertrain The crank sensor signal line is stuck near 0 volts, usually a wire shorted to ground. Often… High P0338 Powertrain The crank signal line sits at 5 or 12 volts and stops switching: open ground, open wire… High P0339 Powertrain The crank signal drops out for moments at a time. Classic sign: stalls when hot, restarts once… High P0340 Powertrain The computer lost the camshaft signal on bank 1. Expect long cranking, less power… Moderate P0341 Powertrain The bank 1 cam signal lands at the wrong crank angle, often from a stretched chain or a sticky… Moderate P0342 Powertrain The bank 1 cam sensor signal stays near 0 volts. Often a weak battery, a pinched wire… Moderate P0343 Powertrain The bank 1 cam signal is stuck high: an unlatched connector, broken ground or open wire after… Moderate