GM Service Manual Online
For 1990-2009 cars only

Important: The following steps need to be completed before using the symptom tables.

  1. Perform the Vehicle Control System Diagnostic System Check. Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information in order to verify that all of the following are true:
  2.    • There are no DTCs set.
       • The control modules can communicate via the serial data link.
  3. Review the system operation in order to become familiar with the system functions. Refer to Cooling System Description and Operation .

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
    • Inspect the surge tank reservoir for the proper coolant level.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

    •  Engine Coolant Temperature Indicator Always On
    •  Low Engine Coolant Indicator Always On
    •  Cooling Fan Always On
    •  Cooling Fan Inoperative
    •  Engine Overheating
    •  Loss of Coolant
    •  Thermostat Diagnosis
    •  Coolant Heater Inoperative
    •  Engine Fails To Reach Normal Operating Temperature