- Strategy Based Diagnosis

The strategy based diagnostic is a uniform approach to repair of all Electrical/Electronic (E/E) systems. The diagnostic flow procedure can always be used to resolve an E/E system problem and is the starting point when repairs are necessary. The steps below are defined to instruct the technician how to proceed with a diagnosis.


1. Verify the Customer Concern

To verify the customer concern, the technician should know the normal operation of the system.

2. Preliminary Checks

Conduct a thorough visual and operational inspection. Review the service history. Detect unusual sounds or odors, and gather diagnostic trouble code information to achieve an effective repair.

3. Diagnostic System Check Testing and Inspectioncontains System Checks where a system may not be supported by one or more DTCs. System checks verify proper operation of the system. This will lead the technician through an organized approach to diagnostics.

4. Check Bulletins and Other Service Information
Other Service Information should include videos, newsletters, and training publications from Pro Service News and OPT, as well as Pulsat broadcasts.

5. Service Diagnostics (Paper/Electronic)

5.1. DTC Stored - Follow the designated DTC chart exactly to make an effective repair.

5.2. Symptom, No DTC - Select the symptom from the symptom tables and follow the diagnostic paths or suggestions to complete the repair. Refer to the applicable component/system check.

5.3. No Published Diagnostics - Analyze the complaint and develop a plan for diagnostics. Utilize the wiring diagrams and theory of operation.


Call technical assistance for similar cases where repair history may be available. Combine technician knowledge with efficient use of the available service information.

5.4. Intermittent - Conditions that are not always present are intermittent. In order to resolve intermittents, perform the following steps:

5.4.1 Observe history DTCs, DTC modes, and the freeze frame data.

5.4.2 Evaluate the symptoms and the conditions described by the customer.

5.4.3 Use a check sheet or other method to identify the circuit or electrical component.

5.4.4 Follow the suggestions for intermittent diagnosis found in the service documentation. The Tech 2 and the Fluke 87 have data capturing capabilities that can assist in detection of intermittents.

5.5. Vehicle operates as designed/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 condition against another vehicle that is operating normally. The condition may be intermittent. Contact Technical Assistance if the concern is common. Verify the complaint under the conditions described by the customer before releasing the vehicle.

6. Re-examine the Concern

When the complaint cannot be successfully found or isolated, a reevaluation is necessary. The customer concern should be duplicated if possible. The complaint could be intermittent or normal as per 5.3 or 5.5 above.

7. Repair and Verification Tests

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

- Conditions noted by the customer when the problem occurred.

- If a DTC was diagnosed, verity the repair by duplicating the conditions present when the DTC was set as noted in the Freeze Frame data.