Important Preliminary Inspections Before Starting

Before using the Symptom diagnosis, perform the following:

• Perform Diagnostic System Check - Vehicle and verify all of the following items:
  • Engine control module (ECM) and malfunction indicator lamp (MIL) are operating correctly.
  • There are no diagnostic trouble codes (DTCs) stored.
  • Scan tool data is within a normal operating range.
• Verify the customer concern.
• Perform the Visual/Physical Inspection in this section. The visual/physical inspection is extremely important, and can lead to correcting a condition without additional testing. It may also help reveal the cause of an intermittent condition.
• Locate the correct symptom. Perform the tests and inspections associated with the symptom.

Review the entire cooling system operation in order to familiarize yourself with the system functions. Refer to Cooling Fan Description and Operation , and Cooling System Description and Operation .