OBD-II trouble code lookup
Plain-language explanations of generic diagnostic trouble codes: what the code means, common causes, symptoms and what to check first.
Popular codes
- P0300 Random/Multiple Cylinder Misfire Detected
- P0420 Catalyst System Efficiency Below Threshold (Bank 1)
- P0171 System Too Lean (Bank 1)
- P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
- P0455 Evaporative Emission Control System Leak Detected (Large Leak)
- P0299 Turbocharger/Supercharger Underboost
- P0016 Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)
- P0401 Exhaust Gas Recirculation Flow Insufficient Detected
- P0335 Crankshaft Position Sensor "A" Circuit
- P0562 System Voltage Low
- U0100 Lost Communication With ECM/PCM "A"
- P0700 Transmission Control System (MIL Request)
Code systems
PPowertrainEngine, fuel, ignition, emissions and transmission.BBodyAirbags, seats, lighting, climate and other body systems. Most B codes are manufacturer-specific.CChassisABS, traction control, steering and suspension. Most C codes are manufacturer-specific.UNetworkCommunication between control modules on the vehicle network.
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How to read a code
Every OBD-II code has five characters. The first letter shows the system: P powertrain, B body, C chassis, U network. The first digit tells whether the code is generic (0, and most 2 codes) or manufacturer-specific (1, and some 3 codes). The remaining digits identify the circuit or condition.
Example: P0301 is a generic powertrain code for a misfire in cylinder 1.