Description of On-Board Diagnostics

DIAGNOSIS AND TESTING ON-BOARD DIAGNOSTICS (OBD) COOLING SYSTEM RELATED DIAGNOSTICS

The powertrain control module (PCM) has been programmed to monitor certain cooling system components:
^ If the engine has remained cool for too long a period, such as with a stuck open thermostat, a Diagnostic Trouble Code (DTC) can be set.
^ If an open or shorted condition has developed in the relay circuit controlling the electric radiator fan, a Diagnostic Trouble Code (DTC) can be set.

If the problem is sensed in a monitored circuit often enough to indicated an actual problem, a DTC is stored. The DTC will be stored in the PCM memory for eventual display to the service technician.

ACCESSING DIAGNOSTIC TROUBLE CODES
To read DTCs and to obtain cooling system data, Refer to Computer and Control Systems.

ERASING TROUBLE CODES
After the problem has been repaired, use the scan tool to erase a DTC.