What does your fault code mean?
What does your fault code mean?
Free OBD2 fault code lookup
A diagnostic trouble code (DTC) is your car's way of telling you something needs attention. This free lookup covers the 200 most common OBD2 fault codes — plain-English meanings, causes, severity, and what to do next.
254 codes found
No codes match your search. Try a different code or check the spelling.
- P0121 OBD-II code P0121 means the throttle position sensor A signal is present but doesn't correlate with expected throttle movement — usually a worn sensor track or dirty throttle body. Air IntakeMedium
- P0122 OBD-II code P0122 means the throttle position sensor A is reporting a signal lower than possible — typically a shorted signal wire or a bad sensor. Air IntakeHigh
- P0123 OBD-II code P0123 means the throttle position sensor A is reporting a signal higher than possible — typically an open ground or a failed sensor. Air IntakeHigh
- P0125 OBD-II code P0125 means the coolant is not reaching the temperature needed for closed-loop fuel control — the engine stays in open-loop enrichment for too long. Engine/PowertrainLow
- P0128 OBD-II code P0128 means the engine is not reaching operating temperature within the expected time — almost always a stuck-open thermostat. Engine/PowertrainLow
- P0130 OBD-II code P0130 flags a generic fault in the upstream O2 sensor circuit on bank 1 — the signal is out of range or invalid but not specifically stuck low or high. EmissionsMedium
- P0131 OBD-II code P0131 means the upstream oxygen sensor on bank 1 is reading persistently low voltage — usually a real lean condition or a dead sensor. EmissionsMedium
- P0132 OBD-II code P0132 means the upstream oxygen sensor on bank 1 is reading persistently high voltage — usually a real rich condition or a shorted sensor. EmissionsMedium
- P0133 OBD-II code P0133 means the upstream O2 sensor on bank 1 is responding too slowly — the sensor is ageing and can no longer switch fast enough for accurate fuel trim. EmissionsMedium
- P0134 OBD-II code P0134 means the upstream bank 1 O2 sensor signal is flatlined — the PCM sees no switching activity, so it can't run closed-loop fuel control. EmissionsMedium
- P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) EmissionsLow
- P0137 OBD-II code P0137 means the downstream O2 sensor on bank 1 is reading persistently low voltage — usually a bad sensor or a real lean exhaust condition. EmissionsLow
- P0138 OBD-II code P0138 means the downstream oxygen sensor on bank 1 is reading persistently high voltage — either a bad sensor or the catalyst is passing rich exhaust. EmissionsLow
- P0140 OBD-II code P0140 means the downstream bank 1 O2 sensor signal is flatlined — the PCM sees no activity, so catalyst efficiency monitoring can't run. EmissionsLow
- P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) EmissionsLow
- P0151 OBD-II code P0151 means the upstream oxygen sensor on bank 2 is reading persistently low voltage — usually a real lean condition or a dead sensor. EmissionsMedium
- P0152 OBD-II code P0152 means the upstream oxygen sensor on bank 2 is reading persistently high voltage — usually a real rich condition or a shorted sensor. EmissionsMedium
- P0155 OBD-II code P0155 flags a fault in the upstream O2 sensor heater circuit on bank 2 — the sensor can't reach operating temperature fast enough for closed-loop control. EmissionsLow
- P0170 OBD-II code P0170 flags a general fuel trim malfunction on bank 1 — the PCM's fuel-trim compensation has hit its limit in either the lean or rich direction. Fuel SystemMedium
- P0171 Fuel Trim System Too Lean (Bank 1) Fuel SystemMedium
- P0172 Fuel Trim System Too Rich (Bank 1) Fuel SystemMedium
- P0174 OBD-II code P0174 means the PCM is adding significant extra fuel on bank 2 to keep the mixture stoichiometric — the engine is running lean with fuel trims maxed out. Fuel SystemMedium
- P0175 OBD-II code P0175 means the PCM is pulling significant fuel out on bank 2 but can't compensate — the engine is running rich and fuel trims are maxed out negative. Fuel SystemMedium
- P0299 Turbocharger/Supercharger A Underboost Condition Turbo/BoostMedium
- P0300 Random/Multiple Cylinder Misfire Detected IgnitionMedium
- P0301 OBD-II code P0301 means the PCM has detected misfires on cylinder 1 — an ignition, fuel, or compression problem is stopping that cylinder from firing properly. IgnitionHigh
- P0302 Cylinder 2 Misfire Detected IgnitionMedium
- P0303 OBD-II code P0303 means the PCM has detected misfires on cylinder 3 — an ignition, fuel, or compression problem is stopping that cylinder from firing properly. IgnitionHigh
- P0304 OBD-II code P0304 means the PCM has detected misfires on cylinder 4 — an ignition, fuel, or compression problem is stopping that cylinder from firing properly. IgnitionHigh
- P0305 OBD-II code P0305 means the PCM has detected misfires on cylinder 5 — an ignition, fuel, or compression problem is stopping that cylinder from firing properly. IgnitionHigh
- P0306 OBD-II code P0306 means the PCM has detected misfires on cylinder 6 — an ignition, fuel, or compression problem is stopping that cylinder from firing properly. IgnitionHigh
- P0307 OBD-II code P0307 means the PCM has detected misfires on cylinder 7 — an ignition, fuel, or compression problem is stopping that cylinder from firing properly. IgnitionHigh
- P0308 OBD-II code P0308 means the PCM has detected misfires on cylinder 8 — an ignition, fuel, or compression problem is stopping that cylinder from firing properly. IgnitionHigh
- P0316 OBD-II code P0316 flags a misfire during the first 1000 crankshaft revolutions after start — usually a cold-start ignition or fuel issue that stabilises once warm. IgnitionMedium
- P0325 OBD-II code P0325 means the PCM has detected a fault in the bank 1 knock sensor circuit — the engine can't retard timing to prevent detonation. IgnitionMedium
- P0335 Crankshaft Position Sensor A Circuit Malfunction Engine/PowertrainHigh
- P0336 OBD-II code P0336 flags an implausible crankshaft position sensor signal — the pattern doesn't match expected engine rotation. Engine/PowertrainHigh
- P0337 OBD-II code P0337 flags a low or missing signal from the crankshaft position sensor — the PCM isn't getting a valid crank reference for ignition and injection timing. Engine/PowertrainHigh
- P0340 OBD-II code P0340 flags a fault in the camshaft position sensor circuit — the PCM cannot see cam position, which affects ignition and injection timing. Engine/PowertrainHigh
- P0341 OBD-II code P0341 means the camshaft position sensor signal is present but implausible — the pattern doesn't match the expected engine phase. Engine/PowertrainMedium
- P0351 OBD-II code P0351 flags a fault in ignition coil A — either the primary drive circuit is bad or the secondary spark path has failed. IgnitionMedium
- P0352 OBD-II code P0352 flags a fault in ignition coil B — either the primary drive circuit is bad or the secondary spark path has failed. IgnitionMedium
- P0400 OBD-II code P0400 flags an EGR flow fault — the PCM commanded EGR but doesn't see the expected change in engine load or flow feedback. EmissionsMedium
- P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient Detected EmissionsMedium
- P0402 OBD-II code P0402 flags excessive EGR flow — the EGR valve is admitting more exhaust than the PCM commanded, causing rough running and driveability issues. EmissionsMedium
- P0403 OBD-II code P0403 means the PCM has detected an electrical fault in the EGR control circuit — the EGR valve isn't responding to commands from the PCM. EmissionsMedium
- P0410 OBD-II code P0410 flags a general fault in the secondary air injection system — the PCM commanded air injection but doesn't see the expected O2 response at cold start. EmissionsLow
- P0411 OBD-II code P0411 means the secondary air injection pump isn't delivering the airflow the PCM commanded — cold-start emissions can't be cleaned up quickly. EmissionsLow
- P0420 OBD-II code P0420 means the bank 1 catalytic converter isn't reducing emissions enough — the downstream O2 sensor reads nearly identically to the upstream one. EmissionsMedium
- P0421 OBD-II code P0421 means the warm-up (close-coupled) catalyst on bank 1 has fallen below efficiency threshold during cold-start emissions monitoring. EmissionsMedium