Description of On-Board Diagnostics

General Information
The PCM monitors critical input and output circuits of the charging system, making sure they are operational. A DTC is assigned to each input and output circuit monitored by the On-Board Diagnostic (OBD) system. Some circuits are checked continuously and some are checked only under certain conditions.

If the OBD system senses that a monitored circuit is bad, it will put a DTC into electronic memory. The DTC will stay in electronic memory as long as the circuit continues to be bad. The PCM is programmed to clear the DTC's from memory after 40 engine warm-up cycles if the problem does not occur again. The DRB scan tool may also be used to erase a DTC.

Diagnostic trouble codes are the results of a system or circuit failure, but do not directly identify the failed component or components.

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

The preferred and most accurate method of retrieving a DTC is by using the DRB scan tool. The scan tool supplies detailed diagnostic information which can be used to more accurately diagnose causes for a DTC.

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

Charging System Diagnostic Trouble Code Descriptions:

NOTE: For a list of DTC's, refer to the charts.

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 DTC's using DRB Scan Tool
1. Connect the DRB 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.
2. Turn the ignition switch on and access the "Read Fault" screen.
3. Record all the DTC's and "freeze frame" information shown on the DRB scan tool.
4. To erase DTC's, use the "Erase Trouble Code" data screen on the DRB scan tool. Do not erase any DTC's until problems have been investigated and repairs have been performed.

* Check Engine Lamp (MIL) will not illuminate if this Diagnostic Trouble Code was recorded.