Reading and Clearing Diagnostic Trouble Codes

A Diagnostic Trouble Code (DTC) indicates the PCM has recognized an abnormal condition in the system.

Remember that DTCs are the results of a system or circuit failure, but do not directly identify the failed component or components.

BULB CHECK
Each time the ignition key is turned to the ON position, the malfunction indicator (check engine) lamp on the instrument panel should illuminate for approximately 2 seconds then go out. This is done for a bulb check.

OBTAINING DTCS
1. Obtain the applicable Powertrain Diagnostic Information.
2. Obtain the appropriate scan tool.
3. Connect the appropriate scan tool to the data link (diagnostic) connector. This connector is located in the passenger compartment; at the lower edge of instrument panel; near the steering column.
4. Turn the ignition switch on and access the Read Fault screen.
5. Record all the DTCs and freeze frame information shown on the appropriate scan tool.
6. To erase DTCs, use the Erase Trouble Code data screen on the appropriate scan tool. Do not erase any DTCs until problems have been investigated and repairs have been performed.

With OBD II, different DTC faults have different priorities according to regulations. As a result, the priorities determine MIL illumination and DTC erasure. DTCs are entered according to individual priority. DTCs with a higher priority overwrite lower priority DTCs.