For 1990-2009 cars

The strategy-based diagnostic is a uniform approach to repair all electrical/electronic (E/E) systems. The diagnostic flow can always be used to resolve an E/E system problem and is a starting point when repairs are necessary. The following steps will instruct the technician on how to proceed with a diagnosis:

• | Verify the customer complaint. To verify the customer complaint, the technician should know the normal operation of the system.

• | Perform preliminary checks as follows:

- | Conduct a thorough visual inspection.

- | Review the service history.

- | Detect unusual sounds or odors.

- | Gather diagnostic trouble code (DTC) information to achieve an effective repair.

• | Check bulletins and other service information. This includes videos, newsletters, etc.

• | Refer to service information, manual, system checks.

• | Refer to service diagnostics.

### No Trouble Found

This condition exists when the vehicle is found to operate normally. The condition described by the customer may be normal. Verify the customer complaint against another vehicle that is operating normally. The condition may be intermittent. Verify the complaint under the conditions described by the customer before releasing the vehicle.

Re-examine the complaint.

When the complaint cannot be successfully found or isolated, a re-evaluation is necessary. The complaint should be re-verified and could be intermittent as defined in Intermittents, or could be normal.

After isolating the cause, the repairs should be made. Validate for proper operation and verify that the symptom has been corrected. This may involve road testing or other methods to verify that the complaint has been resolved under the following conditions:

• | Conditions noted by the customer

• | If a DTC was diagnosed, verify a repair by duplicating conditions present when the DTC was set as noted in the Failure Records or Freeze Frame data.

### Verifying Vehicle Repair

Verification of the vehicle repair will be more comprehensive for vehicles with on-board diagnostic (EOBD) system diagnostics. Following a repair, the technician should perform these steps:

| Important: Follow the steps below when you verify repairs on EOBD systems. Failure to follow these steps could result in unnecessary repairs.

• | Review and record the Failure Records and the Freeze Frame data for the DTC which has been diagnosed. Freeze Fame data will only be stored for an A or B type diagnostic and only if the MIL has been requested.

• | Clear the DTCs.

• | Operate the vehicle within conditions noted in the Failure Records and Freeze Frame data.

• | Monitor the DTC status information for the specific DTC which has been diagnosed until the diagnostic test associated with that DTC runs.