Free Lookup Tool

OBD2 Fault Code Lookup

Enter your diagnostic trouble code (DTC) below to find out what it means and how serious it is. Search by code (P0300, C0035) or keyword (misfire, ABS, oxygen sensor).

What Is an OBD2 Code?

OBD2 (On-Board Diagnostics) codes are the car's way of telling you something is wrong. The system monitors the engine, transmission, and emissions systems. When a sensor reports data outside of normal operating limits, a code is stored and the check engine light is usually triggered. You need an OBD2 reader or scanner to retrieve codes from the car's ECU.

Understanding the Format

Every OBD2 code follows a standard structure:

First letter: System, P Powertrain, B Body, C Chassis, U Network
Second digit: 0 = generic (all vehicles), 1–3 = manufacturer-specific
Third digit: Sub-system (1=fuel/air, 2=ignition, 3=emissions, etc.)
Last two digits: Specific fault number

Code Categories

P Codes, Powertrain Engine, transmission, fuel system. The most common codes. Includes misfires (P0300–P0306), O2 sensors (P0130–P0141), catalytic converter (P0420), and EVAP/emissions codes.

B Codes, Body Airbag/SRS, body control module, lighting, climate control, and windows. B codes often relate to safety systems and should be investigated promptly.

C Codes, Chassis ABS, traction control, stability control (ESP), suspension, and steering. C codes typically affect the car's braking and stability systems.

U Codes, Network CAN bus and module communication faults. U codes indicate that control modules have lost communication with each other, often caused by wiring issues or a faulty module.

Severity Guide

High Severity

Stop driving or drive to a garage immediately. Codes in this category can cause engine damage, complete failure, or safety hazards if ignored. Examples: oil pressure, coolant overtemperature, ABS faults, airbag faults, misfires.

Medium Severity

Book a garage appointment soon, within a week. The car may drive, but performance may be affected and leaving it can cause further damage. Examples: MAF sensor, O2 sensor, EGR faults, transmission codes.

Low Severity

Can wait for your next service, but should not be ignored indefinitely. Usually emissions-related faults or minor sensor issues that won't immediately affect drivability. Examples: EVAP/fuel cap, washer fluid sensor.

Important: This tool provides general descriptions for common OBD2 codes. The same code can have multiple causes and symptoms depending on your vehicle make, model, and year. Always have your car inspected by a qualified mechanic before attempting repairs. Clearing a fault code without fixing the underlying cause will only turn the warning light off temporarily, the code will return.