Symptoms Verification: Notes

Before using the Symptom tables, perform the following inspections:

• Verify that the engine control module (ECM) and malfunction indicator lamp (MIL) are operating correctly. Use the scan tool to turn the MIL ON and OFF.
• Verify that there are no DTCs that are stored.
• Verify that the scan tool data is within a normal operating range.
• Verify the customer concern. Compare the vehicle with a similar unit to help verify the vehicle has an actual problem.
• 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.

Identifying Intermittent Conditions 

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

• Moisture and water intrusion in connectors, terminals and components
• Incomplete connector mating
• Poor 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 too short or tight.
• Wire insulation that is chaffed or cut.
• 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 surfaces
• Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge
• Incorrect installation of aftermarket, add on accessories