GM Service Manual Online
For 1990-2009 cars only

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

  1. Perform the Diagnostic System Check - Engine Cooling before using the Symptom Tables in order to verify that all of the following are true:
  2. There are no DTCs set.
  3. The control modules can communicate through the serial data link.

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect cooling system operation. 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.

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:

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