OBD-II code reference
Trouble code lookup
Here are the 150 most-searched OBD-II codes — the ones that most often trigger a Check Engine light: misfires, catalyst efficiency, EVAP leaks, oxygen sensors. The full 1947-code library — including rare U-network codes and every P2xxx — is available in the app and via subscription.
- 1947
- codes in the library
- 150
- popular codes free to browse
- 1797
- codes in the app and via subscription
Popular codes — free to browse
Camshaft and VVT
9
-
P0011 WarningIntake camshaft on Bank 1 is advanced beyond the commanded angle — VVT actuator over-shot the target position. Symptoms: hard cold start, drops in power, poor idle quality - P0012 WarningIntake camshaft on Bank 1 is retarded from the commanded angle — VVT can't reach full advance. Symptoms: sluggish throttle response, rough idle, occasional stall on cold start
- P0013 WarningOpen or short in the exhaust VVT actuator solenoid circuit on Bank 1. Engine can't control exhaust cam phasing
- P0014 WarningExhaust camshaft on Bank 1 is over-advanced. Only Bank 1 is monitored on V-engines. Symptoms mirror P0011 but from the exhaust side
- P0015 WarningExhaust camshaft on Bank 1 is retarded from commanded angle. Typical after significant mileage or long oil change intervals
- P0016 WarningCorrelation between crankshaft and intake camshaft on Bank 1 is out of spec. ECM sees the two sensors reporting mismatched positions — timing is physically off
- P0017 WarningCorrelation between crankshaft and exhaust camshaft on Bank 1 is out of spec. The two sensors disagree beyond the accepted window
- P0018 WarningCorrelation between crankshaft and intake camshaft on Bank 2 is out of spec. V6, V8, W-engines only
- P0019 WarningCorrelation between crankshaft and exhaust camshaft on Bank 2 is out of spec. V6, V8, W engines only
Crankshaft position sensor
6
-
P0335 WarningCrankshaft Position Sensor (CKP) circuit fault — signal missing or unstable. Engine may not start at all, may stall while driving, or run with dropouts - P0336 WarningCKP sensor signal is out of expected range. Engine occasionally stalls or is hard to start when hot
- P0340 WarningCamshaft Position Sensor (CMP) circuit fault. Engine doesn't know when to inject fuel to specific cylinders — falls back to synchronous injection, fuel economy worsens
- P0341 WarningCMP signal doesn't match expected range. Engine sees camshaft phasing drifting
- P0342 CriticalCamshaft Position Sensor 'A' Circuit Low
- P0343 CriticalCamshaft Position Sensor 'A' Circuit High
MAF sensor
7
-
P0100 WarningMass Air Flow (MAF) sensor circuit malfunction. ECM can't read airflow properly — falls back to a rough model, drivability suffers - P0101 WarningMAF sensor readings out of expected range. Airflow doesn't match engine load — ECM knows something is off but can't fault the sensor directly
- P0102 WarningLow input from MAF sensor. ECM sees less airflow than physically possible, or an open circuit
- P0103 WarningMass or Volume Air Flow Circuit High Input
- P0104 WarningMass or Volume Air Flow Circuit Intermittent
- P0105 WarningManifold Absolute Pressure/Barometric Pressure Circuit
- P0106 WarningManifold Absolute Pressure/Barometric Pressure Circuit Range/Performance
MAP sensor
4
-
P0107 WarningLow input from Manifold Absolute Pressure (MAP) sensor. Voltage below expected range — ECM can't calculate cylinder fill - P0108 WarningHigh input from MAP sensor. ECM sees higher intake pressure than the engine could actually produce
- P0234 WarningTurbocharger Overboost Condition
- P0299 WarningTurbocharger Underboost Condition
IAT sensor
2
Thermostat and cooling
4
-
P0117 WarningLow input from Engine Coolant Temperature (ECT) sensor. ECM thinks the engine is running at 140°C and activates cooling aggressively - P0118 WarningHigh input from ECT sensor. ECM sees sub-zero coolant temp and over-fuels. Dash gauge may read at zero
- P0125 WarningCoolant temperature isn't rising fast enough to enter closed-loop fuel control. Engine takes forever to warm up, ECM stays in enriched open-loop — fuel economy tanks
- P0128 InformationalCoolant temperature hasn't reached normal operating range (87–92°C) in the expected time. Engine warms slowly or never fully warms — gauge stalls at 60–70°C
Throttle body
3
-
P0121 WarningThrottle/Pedal Position Sensor/Switch 'A' Circuit Range/Performance - P0122 WarningLow input from Throttle Position Sensor (TPS). Pedal is pressed but sensor reports zero — ECM enters limp mode
- P0123 WarningHigh input from TPS. Pedal released but sensor reports wide open — engine won't respond to pedal correctly
Oxygen sensors
12
-
P0130 WarningO2 Sensor Circuit (Bank 1, Sensor 1) — upstream sensor malfunction - P0131 WarningLow input from Bank 1 Sensor 1 O2 sensor (upstream). ECM sees the sensor stuck on lean without switching
- P0132 WarningHigh input from Bank 1 Sensor 1. Sensor stuck on rich — voltage above 0.9V constantly
- P0133 WarningSlow response from Bank 1 Sensor 1. Sensor still works but responds slower than spec — fewer than 8 rich/lean switches per minute
- P0134 WarningO2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
- P0135 WarningHeater malfunction on Bank 1 Sensor 1. Sensor works but its heater isn't drawing current — sensor never reaches operating temperature
- P0136 WarningO2 Sensor Circuit (Bank 1, Sensor 2) — downstream sensor malfunction
- P0137 WarningLow input from Bank 1 Sensor 2 (downstream O2). This sensor is used to monitor the catalytic converter — readings are abnormally low
- P0138 WarningHigh input from Bank 1 Sensor 2. Constantly high voltage — either the catalyst isn't working, or the sensor is faulty
- P0139 WarningO2 Sensor Circuit Slow OBDResponse
- P0140 WarningNo signal from Bank 1 Sensor 2 (open circuit). Sensor sends no signal to ECM at all
- P0141 WarningHeater malfunction on Bank 1 Sensor 2. Sensor present but not heating — takes too long to reach operating temperature or doesn't reach at all
Fuel injectors and trim
16
-
P0171 WarningSystem too lean, Bank 1 — engine is running out of fuel margin; ECM has been compensating but has hit its correction limit (LTFT > +25%) - P0172 WarningSystem too rich, Bank 1 — engine getting more fuel than needed; ECM has been subtracting but can't correct enough (LTFT < -25%)
- P0174 WarningSystem too lean, Bank 2. V6/V8 only. Same symptoms as P0171 but on the other cylinder bank
- P0175 WarningSystem too rich, Bank 2. V-engines only. Bank 2 analog of P0172
- P0201 WarningInjector Circuit Malfunction - Cylinder 1
- P0202 WarningInjector Circuit Malfunction - Cylinder 2
- P0203 WarningInjector Circuit Malfunction - Cylinder 3
- P0204 WarningInjector Circuit Malfunction - Cylinder 4
- P0205 WarningInjector Circuit / Open - Cylinder 5
- P0206 WarningInjector Circuit / Open - Cylinder 6
- P0463 WarningFuel Level Sensor 'A' Circuit High
- P0087 WarningFuel Rail/System Pressure - Too Low
- P0088 WarningFuel Rail/System Pressure - Too High
- P0089 WarningFuel Pressure Regulator Performance
- P0090 WarningFuel Pressure Regulator 1 Control Circuit
- P0091 WarningFuel Pressure Regulator 1 Control Circuit Low
Ignition misfires
10
-
P0300 WarningRandom misfire across multiple cylinders — engine shakes at idle, stumbles under load, loses power, Check Engine light on solid or flashing - P0301 WarningMisfire in cylinder 1 — engine loses grunt, hesitates under acceleration, shakes at idle, fuel economy worsens
- P0302 WarningMisfire in cylinder 2 — same diagnosis as P0301 but on cylinder 2. Rough running, power loss
- P0303 WarningMisfire in cylinder 3. Consistent engine shake, most noticeable on cold start
- P0304 WarningMisfire in cylinder 4. Often shows up alone on 4-cylinder engines due to uneven plug wear
- P0305 WarningMisfire in cylinder 5. Applies to 5/6/8-cylinder engines (V6, inline-5, V8)
- P0306 WarningMisfire in cylinder 6. On V6 this is the last cylinder — often wears first due to heat exposure
- P0307 WarningMisfire in cylinder 7. V8 engines only
- P0308 WarningMisfire in cylinder 8. V8 only — often the hottest cylinder on Bank 2
- P0380 CriticalGlow Plug/Heater Circuit 'A'
Knock sensor
3
Ignition coils
9
-
P0350 CriticalPrimary or secondary ignition coil circuit malfunction (generic). Engine isn't getting adequate spark — misfires, poor performance - P0351 CriticalIgnition coil #1 circuit malfunction. Weak or no spark on cylinder 1
- P0352 CriticalIgnition Coil 'B' Primary/Secondary Circuit
- P0353 CriticalIgnition Coil 'C' Primary/Secondary Circuit
- P0354 CriticalIgnition Coil 'D' Primary/Secondary Circuit
- P0355 CriticalIgnition Coil 'E' Primary/Secondary Circuit
- P0356 CriticalIgnition Coil 'F' Primary/Secondary Circuit
- P0357 CriticalIgnition Coil 'G' Primary/Secondary Circuit
- P0358 CriticalIgnition Coil 'H' Primary/Secondary Circuit
EGR valve
5
-
P0401 WarningInsufficient Exhaust Gas Recirculation (EGR) flow — valve isn't delivering the commanded exhaust gas volume to the intake. Common on diesels and turbocharged gasoline engines - P0402 WarningExhaust Gas Recirculation Flow Excessive Detected
- P0403 WarningExhaust Gas Recirculation Control Circuit
- P0404 WarningEGR valve control range out of spec — valve moves, but position doesn't match commanded value. Common past 100K km on diesels
- P0405 WarningLow input from EGR position sensor. ECM isn't getting actual feedback on valve position
Catalytic converter
3
-
P0420 WarningCatalytic converter efficiency below threshold, Bank 1 — the downstream O2 sensor mirrors the upstream too closely, meaning the catalyst is no longer converting the exhaust properly - P0421 WarningWarm Up Catalyst Efficiency Below Threshold
- P0430 WarningCatalytic converter efficiency below threshold, Bank 2 — same as P0420 but for the other cylinder bank (V6, V8, W-engines)
EVAP system
14
-
P0440 InformationalGeneral Evaporative Emission (EVAP) system malfunction. Fuel vapors escape to atmosphere instead of being routed to the intake - P0441 WarningIncorrect purge flow. Purge valve isn't following the ECM's commanded schedule
- P0442 InformationalSmall EVAP leak detected — leak smaller than a 1.0 mm equivalent hole, caught during pressure test. Often triggered in cold weather after cold fuel fill
- P0443 WarningPurge valve control circuit malfunction. ECM can't drive the valve normally
- P0444 WarningEvaporative Emission System Purge Control Valve Circuit Open
- P0445 WarningEvaporative Emission System Purge Control Valve Circuit Shorted
- P0446 InformationalEVAP vent control circuit malfunction. Vent valve won't open/close on command
- P0450 WarningEvaporative Emission System Pressure Sensor/Switch
- P0451 WarningEvaporative Emission System Pressure Sensor/Switch Range/Performance
- P0452 WarningEvaporative Emission System Pressure Sensor/Switch Low
- P0453 WarningEvaporative Emission System Pressure Sensor/Switch High
- P0455 WarningLarge EVAP leak detected — fuel vapors escaping to atmosphere rather than being processed. Big leak, easier to find
- P0456 InformationalVery small EVAP leak detected (under 0.5 mm). Hardest variant to diagnose — needs a smoke machine
- P0457 WarningEvaporative Emission System Leak Detected (fuel cap loose/off)
Vehicle speed sensor
3
Idle air control
3
Automatic transmission
9
-
P0700 WarningTransmission Control Module (TCM) reports a fault in its own subsystem — this is a generic pointer code, real cause is in a specific P07xx-P08xx code. Often accompanied by harsh shifts or limp mode (3rd gear only) - P0705 WarningTransmission Range Sensor Circuit Malfunction (PRNDL Input)
- P0715 WarningInput/Turbine Speed Sensor Circuit Malfunction
- P0720 WarningOutput Speed Sensor Circuit Malfunction
- P0730 WarningIncorrect Gear Ratio
- P0740 WarningTorque Converter Clutch (TCC) circuit open. Lock-up clutch doesn't engage — engine revs high on highway, fuel economy suffers
- P0741 WarningTCC clutch slipping or stuck in wrong position. Highway feels 'rubbery' — RPM floats at constant speed
- P0742 WarningTCC clutch stuck engaged. Vehicle stalls at stops like a manual — classic symptom
- P0743 WarningTorque Converter Clutch Circuit Electrical
Airbag module (SRS)
1
ABS wheel sensors
4
-
C0035 CriticalLeft front wheel speed sensor circuit malfunction (ABS). ABS, ESP, cruise control may not work. ABS light on the dash - C0040 CriticalRight front wheel speed sensor circuit malfunction. Same as C0035 but on the other side
- C0045 CriticalLeft Rear Wheel Speed Sensor Circuit Malfunction
- C0050 CriticalRight Rear Wheel Speed Sensor Circuit Malfunction
CAN network and ECU
23
-
P0562 WarningSystem Voltage Low - P0563 WarningSystem Voltage High
- P0601 WarningInternal Control Module Memory Check Sum Error
- P0602 CriticalControl Module Programming Error
- P0603 WarningInternal Control Module Keep Alive Memory (KAM) Error
- P0604 WarningInternal Control Module Random Access Memory (RAM) Error
- P0605 WarningInternal Control Module Read Only Memory (ROM) Error
- P0606 CriticalECM/PCM Processor
- U0001 CriticalHigh Speed CAN Communication Bus
- U0073 CriticalControl Module Communication Bus A Off
- U0100 CriticalLost communication with Engine Control Module (ECM/PCM) over CAN bus. Dash may show errors, no tach, engine may not start
- U0101 CriticalLost communication with Transmission Control Module (TCM) over CAN. Transmission goes to limp mode (3rd gear only)
- U0102 CriticalLost Communication with Transfer Case Control Module
- U0104 CriticalLost Communication With Cruise Control Module
- U0111 CriticalLost Communication With Battery Energy Control Module 'A'
- U0121 CriticalLost communication with ABS control module. ABS, ESP, stability control non-functional — ABS warning light
- U0126 CriticalLost Communication With Steering Angle Sensor Module
- U0131 CriticalLost Communication With Power Steering Control Module
- U0140 CriticalLost communication with Body Control Module (BCM). Windows, mirrors, central lock, lighting may all fail
- U0141 CriticalLost Communication With Body Control Module 'A'
- U0151 CriticalLost Communication With Restraints Control Module
- U0155 WarningLost communication with Instrument Panel Cluster (IPC). Speedometer, tachometer, fuel gauge don't show data
- U0164 CriticalLost Communication With HVAC Control Module