Diagnostic Strategies
STRATEGY-BASED DIAGNOSTICSStrategy-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 following steps will instruct the technician how to proceed with a diagnosis:
1. Verify the customer complaint.
- To verify the customer complaint, the technician should know the normal operation of the system.
2. Perform preliminary checks.
- Conduct a thorough visual inspection.
- Review the service history.
- Detect unusual sounds or odors.
- Gather diagnostic trouble code information to achieve an effective repair.
3. Check bulletins and other service information.
- This includes videos, newsletters, etc.
DTC Stored
Follow the designated DTC chart exactly to make an effective repair.
No DTC
Select the symptom from the symptom tables. Follow the diagnostic paths or suggestions to complete the repair. You may refer to the applicable component/system check in the system checks.
No Matching Symptom
1. Analyze the complaint.
2. Develop a plan for diagnostics.
3. Utilize the wiring diagrams and the 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.
Intermittents
Conditions that are not always present are called intermittents. To resolve intermittents, perform the following steps:
1. Observe history DTCs.
2. Evaluate the symptoms and the conditions described by the customer.
3. Use a check sheet or other method to identify the circuit or electrical system component.
4. Follow the suggestions for intermittent diagnosis found in the service documentation.
Most scan tool, such as the Tech II have data- capturing capabilities that can assist in detecting intermittents.
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.
1. 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.
2. Repair and verify.
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.
Verifying Vehicle Repair
Verification of vehicle repair will be more comprehensive for vehicles with OBD system diagnostic. Following a repair, the technician should perform the following steps:
1. Review and record the Fail Records for the DTC which has been diagnosed.
2. Clear DTC (s).
3. Operate the vehicle within conditions noted in the Fail Records.
4. Monitor the DTC status information for the specific DTC which has been diagnosed until the diagnostic test associated with that DTC runs.
Following these steps are very important in verifying repairs on OBD systems. Failure to follow these steps could result in unnecessary repairs.
WARNING:
HIGH VOLTAGE IS APPLIED TO THE
HARNESS CONNECTED TO ECM COMMON 1,
COMMON 2, AND TWV No.1 TO No.8
SUFFICIENT CARE SHOULD BE TAKEN NOT
TO GET AN ELECTRIC SHOCK.