- Flow of Diagnosis - Start Here

Diagnostic Chart:

Strategy Based Diagnostics
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 steps below are defined to instruct the technician how to proceed with a diagnosis.

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

Preliminary Checks
1. Conduct a thorough visual inspection.
2. Review the service history
3. Detect unusual sounds or odors
4. Gather diagnostic trouble code information in order to achieve an effective repair.

Check Technical Service Bulletins
Technical Service Bulletins provide updated service and repair information including recalls.

Service Information System Checks
A system may be supported by one or more Diagnostic Trouble Codes (DTCs). System checks verify the proper operation of the system. This will lead the technician in an organized approach to diagnosis.

Service Diagnostics
1. DTC Stored - Follow the designated DTC chart exactly to make an effective repair.

2. No DTC - Select the symptom from the Symptom Tables in Computers and Control System and follow the diagnostic paths or suggestions to complete the repair, or refer to the applicable component/system check.

3. No Matching Symptom - Analyze the complaint and develop a plan for diagnostics. Utilize the wiring diagrams and theory of operation. Combine technician knowledge with efficient use of the available service information.

4. Intermittent - Conditions that are not always present are intermittent. To resolve intermittents, perform the following steps:

4.1 Observe history DTCs, DTC modes and freeze frame data.

4.2 Evaluate the symptoms and conditions described by the customer.

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

4.4 Follow the suggestions for intermittent diagnosis found in Symptoms.

4.5 The Tech 1, Tech 2 and Fluke 87 have data capturing capabilities that can assist in detection of intermittents.

5. Vehicle operates as designed/No trouble found

6. Search vehicle histories for similar cases. Combine technician knowledge with efficient use of the available service information.

6.1. This condition exists when the vehicle is found to operate normally.

6.2. The condition described by the customer may be normal. Verify against another vehicle that is operating normally.

6.3. The condition may be intermittent. Verify the complaint under the conditions described by the customer before releasing the vehicle.

Re-examine the Concern
When the complaint cannot be successfully found or isolated, a reevaluation is necessary. The complaint should be re-verified and could be intermittent or normal .

Repair and Verification Tests
After isolating the cause, the repairs 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.