For 1990-2009 cars

### 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:

- | Ensure that the engine control module (ECM) and indicator lamp are operating correctly.

- | Ensure that there are no diagnostic trouble codes (DTCs) that are 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 system operation in order to familiarize yourself with the system functions.

### Visual/Physical Inspection

Notice: Use the connector test adapter kit J 35616-A for any test that requires probing the following items:

• | The PCM harness connectors

• | The electrical center fuse/relay cavities

• | The component terminals

• | The component harness connector

Using this kit will prevent damage caused by the improper probing of connector terminals.

Several of the symptom procedures call for a careful visual and physical inspection. This can lead to correcting a condition without further tests and can save time. This inspection should include the following areas:

• | Ensure that the ECM grounds are clean, tight, and correctly located.

• | Inspect cooling system hoses and pipes for splits, kinks, and proper connections. Inspect thoroughly for any type of a leak or a restriction.

• | Inspect for a dirty or restricted radiator and HVAC condenser.

• | Inspect for aftermarket devices which could affect the operation of the Cooling System.

• | 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.

### Identifying Intermittent Conditions

Many intermittent conditions occur with harness or connector movement due to engine torque, rough pavement, vibration or physical movement of a component. Refer to the following for a list to help determine an intermittent condition:

• | Moisture and water intrusion in connectors, terminals, and components

• | Connector mating

• | Terminal contact

• | High circuit or component resistance--High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component.

• | Harness that is located too tight, or chaffed circuits

• | High or low ambient temperature

• | High or low engine coolant temperatures

• | High underhood temperatures

• | Heat build up in component or circuit due to circuit resistance, poor terminal contact, or high electrical load

• | High or low system voltage

• | High vehicle load conditions

• | Rough road surface

• | Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge

• | Incorrect installation of non-factory, aftermarket, and after factory add on accessories

If an intermittent is determined, refer to Testing for Intermittent Conditions and Poor Connections for specific strategies in diagnosing intermittent conditions.

### Symptom List

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

• | Cooling Fan Always On

• | Cooling Fan Inoperative

• | Engine Overheating

• | Loss of Coolant

• | Thermostat Diagnosis

• | Engine Fails To Reach Normal Operating Temperature