Look up any check engine code.
Find what an OBD2 code means, how serious it is, whether you can keep driving, the most likely causes ranked by frequency, and a real repair-cost range — scoped to your exact year, make, and model.
What is an OBD2 code?
An OBD2 code — also called a DTC (Diagnostic Trouble Code) — is a five-character code your car’s computer stores when it detects a fault. The first letter is the system (P = powertrain, B = body, C = chassis, U = network) and the digits identify the specific problem. For example, P0420 means the catalytic converter is below its efficiency threshold. A code tells you where to look — confirming the actual cause still takes diagnosis.
Most common codes
The check engine codes drivers look up most.
- P0420 Catalyst Efficiency Below Threshold
- P0300 Random or Multiple Cylinder Misfire
- P0301 Cylinder 1 Misfire
- P0171 Fuel System Too Lean (Bank 1)
- P0440 EVAP System Malfunction (Generic)
- P0455 EVAP Large or Gross Leak Detected
- P0128 Engine Not Reaching Operating Temperature
- P0401 EGR Flow Insufficient
- P0700 Transmission Control System Malfunction
- P0131 O2 Sensor Low Voltage (Bank 1 Upstream)
- P0011 Intake Cam Over-Advanced (Bank 1, VVT)
- P0606 PCM Internal Processor Fault
All OBD2 codes
50 powertrain trouble codes, each with a vehicle-specific diagnosis. Pick a code, then choose your year, make, and model.
- P0011 Intake Cam Over-Advanced (Bank 1, VVT)
- P0012 Intake Cam Over-Retarded (Bank 1, VVT)
- P0013 Exhaust Cam Actuator Circuit Fault (Bank 1)
- P0014 Exhaust Cam Over-Advanced (Bank 1, VVT)
- P0016 Crank/Cam Correlation Fault (Bank 1 Intake)
- P0017 Crank/Cam Correlation (Bank 1 Exhaust)
- P0101 MAF Sensor Range / Performance
- P0102 MAF Sensor Low Input
- P0113 Intake Air Temperature High Input
- P0118 Coolant Temp Sensor High Input
- P0121 Throttle Position Sensor Range / Performance
- P0125 Coolant Too Cold for Closed-Loop Fuel Control
- P0128 Engine Not Reaching Operating Temperature
- P0131 O2 Sensor Low Voltage (Bank 1 Upstream)
- P0133 O2 Sensor Slow Response (Bank 1 Upstream)
- P0135 O2 Sensor Heater Circuit (Bank 1 Upstream)
- P0136 Post-Cat O2 Sensor Circuit Fault (Bank 1)
- P0138 Post-Cat O2 Sensor High Voltage (Bank 1 Downstream)
- P0141 Post-Cat O2 Heater Circuit (Bank 1 Downstream)
- P0171 Fuel System Too Lean (Bank 1)
- P0172 Fuel System Too Rich (Bank 1)
- P0174 Fuel System Too Lean (Bank 2)
- P0300 Random or Multiple Cylinder Misfire
- P0301 Cylinder 1 Misfire
- P0325 Knock Sensor 1 Circuit Fault
- P0335 Crankshaft Position Sensor Circuit Fault
- P0340 Camshaft Position Sensor Circuit Fault
- P0341 Camshaft Position Sensor Range / Performance
- P0401 EGR Flow Insufficient
- P0411 Secondary Air Injection Insufficient Flow
- P0420 Catalyst Efficiency Below Threshold
- P0430 Catalyst Efficiency Below Threshold (Bank 2)
- P0440 EVAP System Malfunction (Generic)
- P0442 EVAP Small Leak Detected
- P0446 EVAP Vent Control Circuit Fault
- P0455 EVAP Large or Gross Leak Detected
- P0456 EVAP Very Small Leak Detected
- P0496 EVAP High Purge Flow / Stuck-Open Purge Valve
- P0497 EVAP Low Purge Flow
- P0500 Vehicle Speed Sensor Malfunction
- P0507 Idle Higher Than Expected
- P0521 Oil Pressure Sensor Range / Performance
- P0606 PCM Internal Processor Fault
- P0700 Transmission Control System Malfunction
- P0720 Transmission Output Speed Sensor Malfunction
- P0741 Torque Converter Clutch Stuck Off
- P0750 Shift Solenoid A Malfunction
- P2096 Post-Cat Trim Lean (Bank 1)
- P2187 System Too Lean at Idle (Bank 1)
- P2270 Post-Cat O2 Stuck Lean (Bank 1 Downstream)
OBD2 code FAQ
- An OBD2 code (also called a DTC, or Diagnostic Trouble Code) is a five-character code your car's computer stores when it detects a fault — for example, P0420 means the catalytic converter is below its efficiency threshold. The letter shows the system (P = powertrain, B = body, C = chassis, U = network) and the digits narrow down the specific fault. A code tells you where to look; confirming the actual cause still takes diagnosis.
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