Diagnostic Trouble Code

Diagnostic trouble codes (DTCs) used in OBD II vehicles will begin with a letter and are followed by four numbers. The letter at the beginning of the DTC identifies the function of the monitored device that has failed. A P indicates a powertrain device, C indicates a chassis device, B is for body device and U indicates a network or data link code. The first number indicates if the code is generic (common to all manufacturers), or if it is manufacturer specific. A 0 indicates generic, 1 indicates manufacturer-specific. The second number indicates the system that is affected with a number between 1-7. The following is a list showing what numbers are assigned to each system.

1. Fuel and air metering
2. Fuel and air metering (injector circuit malfunctions only)
3. Ignition system or misfire
4. Auxiliary emission controls
5. Vehicle speed controls and idle control system
6. Computer output circuits
7. Transmission

The last two numbers of the DTC indicate the component or section of the system where the fault
is located.

Diagnostic Trouble Codes Capable of Illuminating the MIL When Detected on the 1st Trip
Misfire diagnostic trouble codes
Catalyst diagnostic trouble codes
Closed loop control diagnostic trouble codes​