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Fault Diagnosis Strategy For Electronic Systems: Notes

  1. The customer's description of the trouble is the basis of the fault diagnosis strategy. If necessary, the customer must demonstrate the trouble on the car to avoid a misunderstanding.
  2. In certain cases, the function may be operating correctly.
    • Good product knowledge is required to be able to determine if this is the case.
    • If the function is operating correctly, this must be explained to the customer.
  3. If the function is judged to be faulty, the car must be repaired. Saab's fault diagnosis strategy is based on the technician being familiar with the customer's description of the trouble. Therefore, note the complaint and any additional information on the work order.
  4. The technician obtains readouts of the DTCs from all systems. A malfunction in one system may well be caused by a fault in another system.
  5. There may be DTCs in the car that are secondary faults or that are incorrectly set.
    • Compare the customer's complaint with the symptom descriptions of the different DTCs. EPSI has a quick search path for this.
    • If the symptom description of a DTC corresponds with the customer's complaint, this DTC is probably caused by the primary fault. Repair according to the instructions.
  6. If there is no corresponding DTC, the fault can be diagnosed from the symptom.
    • Search the EPSI under fault diagnosis by symptoms in the system where the fault has occurred.
    • If the symptom description in the system concerned corresponds with the complaint, it is probably the correct fault diagnosis description. Repair according to instructions.
  7. Certain fault symptoms can be rectified by reprogramming the control module.
    • Does the customer complaint correspond with a known software problem in a reprogrammed control module?
    • Reprogram the control module as instructed in SPS.
  8. If there is no corresponding DTC or symptom, the technician must diagnose the fault himself. A final check must be made after repairs. Good technical product knowledge is required to solve this kind of problem.
  9. The car is ready.
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