Fault Diagnosis and Customer Handling
Fault Diagnosis and Customer Handling
This domain tests a structured diagnostic process and professional communication. The exam expects you to verify the complaint, gather information, test logically, and explain the repair without jargon.
Core rules
- Interview the customer: when the fault occurs, temperature, speed, load, warnings, recent work, and whether it is constant or intermittent.
- Verify the concern by road test or operation before diagnosis. Write down the symptom, not the customer’s guessed cause.
- Use DTCs as a guide, not a verdict. Check freeze-frame data, live data, and the circuit; confirm the root cause before replacing parts.
- After repair, verify the fix under the original conditions and check that no new codes are set.
- Explain the fault, the evidence, the repair, and the cost in plain language. Document the complaint, cause, and correction on the job card.
Worked example
A customer says the car “fails to start sometimes, usually after short trips.” The battery and starter were replaced elsewhere. Verify by reproducing the fault; check for a security lamp, scan for codes, and inspect the starter control circuit. A voltage drop test at the starter relay and a check of the neutral safety switch may reveal an intermittent open circuit. The diagnosis is based on the reproduced symptom and circuit tests, not on the previous parts. Explain that the earlier parts did not address the cause.
Traps
Replacing parts from a hunch, accepting a customer’s diagnosis as the cause, failing to verify the repair, using jargon, and not recording the three Cs-complaint, cause, and correction. Also, avoid promising a repair before testing.