Diagnostic Strategies
RELATED DIAGNOSTICSThe 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. Refer to Powertrain Management.
ACCESSING DIAGNOSTIC TROUBLE CODES
To read DTC's and to obtain cooling system data, refer to Powertrain Management.
ERASING TROUBLE CODES
After the problem has been repaired, use the DRB scan tool to erase a DTC. Refer to Powertrain Management for operation of the DRB scan tool.
ORB SCAN TOOL
For operation of the DRB scan tool refer to Powertrain Management.
PRELIMINARY CHECKS
ENGINE COOLING SYSTEM OVERHEATING
Establish what driving conditions caused the complaint. Abnormal loads on the cooling system such as the following may be the cause:
PROLONGED IDLE, VERY HIGH AMBIENT TEMPERATURE, SLIGHT TAIL WIND AT IDLE, SLOW TRAFFIC, TRAFFIC JAMS, HIGH SPEED, OR STEEP GRADES.
Driving techniques that avoid overheating are:
^ Idle with A/C off when temperature gauge is at end of normal range.
^ If vehicle is equipped with a 3.9L V-6 or 5.2L/ 5.9L V-8 engine, increasing engine speed for more air flow is recommended.
TRAILER TOWING:
Consult Trailer Towing section of owners manual. Do not exceed limits.
AIR CONDITIONING; ADD-ON OR AFTER MARKET:
A maximum cooling package should have been ordered with vehicle if add-on or after market A/C is installed. If not, maximum cooling system components should be installed for model involved per manufacturer's specifications.
RECENT SERVICE OR ACCIDENT REPAIR:
Determine if any recent service has been performed on vehicle that may effect cooling system. This may be:
^ Engine adjustments (incorrect timing)
^ Slipping engine accessory drive belt(s)
^ Brakes (possibly dragging)
^ Changed parts. Incorrect water pump, or pump rotating in wrong direction due to belt not correctly routed a Reconditioned radiator or cooling system refilling (possibly under filled or air trapped in system).
NOTE: If investigation reveals none of the previous items as a cause for an engine overheating complaint, refer to following Cooling System Diagnosis charts.
These charts are to be used as a quick-reference only. Refer to the text for information.
COOLING SYSTEM DIAGNOSIS CHART