Strategy-Based Diagnostics

CAUTION: Lack of basic knowledge of the Powertrain Control System and diagnostic tools, when performing diagnostic procedures could result in incorrect diagnostic or damage to Powertrain components. Do not attempt to diagnose a Powertrain problem without this basic knowledge.

Strategy Based Diagnostics:

STRATEGY BASED DIAGNOSTICS

NOTE: 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.

1. Verify the Customer Complaint:
- To verify the customer complaint the technician should know the normal operation of the system.

2. Preliminary Checks:
- Conduct a thorough visual inspection, review the service history, detect unusual sounds or odors, and gather diagnostic trouble code information to achieve an effective repair.
- Check Bulletins and Other Service Information.

3. Service Information:
- 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 in an organized approach to diagnostics.

4. Perform System Checks:
a. DTC Stored:
- Follow the designated DTC Table exactly to make an effective repair.
b. No DTC:
- Select the symptom from Diagnosis by Symptom and follow the diagnostic paths or suggestions to complete the repair.
c. No Matching Symptom:
- Analyze the complaint and develop a plan for diagnostics. Utilize the wiring diagrams and theory of operation.
d. Intermittents: (Conditions that are not always present).
- Observe history DTCs, DTC modes and freeze frame data.
- Evaluate the symptoms and conditions described by the customer.
- Use a check sheet or other method to identify the circuit or electrical system component.
- Follow the suggestions for intermittent diagnosis found in the service documentation.

NOTE: The Tech 1, Tech 2 and Fluke 87 scan tools have data capturing capabilities that can assist in detection of Intermittents.

e. 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 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.

5. Re-Examine the Complaint:
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.

6. 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 under the following conditions:
- Conditions noted by the customer.
- If a DTC was diagnosed, verify a repair by duplicating conditions present when a DTC was set as noted in the Fail Records or Freeze Frame data.

NOTE: The underhood "Vehicle Emissions Control Information Label" contains important emission specifications and setting procedures. In the upper left corner is exhaust emission information. This identifies the year, the manufacturing division of the engine, the displacement of the engine in liters, the class of the vehicle, and type of fuel metering system. There is also an illustrated emission components and vacuum hose schematic.