OBD-II Code Lookup
Search thousands of OBD-II diagnostic trouble codes (P0xxx, C0xxx, B0xxx, U0xxx) with meanings, systems, common causes, symptoms and recommended checks.
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Reading OBD-II codes
Codes are read with a scanner plugged into the OBD port. The first letter tells the system: P = powertrain, C = chassis, B = body, U = network. The code is only the starting point — confirm with live data and checks.
- P0300 : random misfire
- P0171 : system too lean (bank 1)
- P0420 : catalyst efficiency below threshold
- P0128 : coolant thermostat below regulating temp
- Always clear codes only after the fault is fixed
FAQ
If the light blinks, that is a severe misfire that can damage the catalytic converter — stop and tow. A steady light with normal driving is less urgent, but read the code soon.
It clears them for a while, but they return if the fault is still present, and it resets all learned settings. Diagnose the cause first.
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