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Diagnosis & Repair

  1. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. After performing OBD system check, go to next step.
  2. Turn ignition on with engine off. If scan tool displays engine data, go to DIAGNOSTIC AIDS. If scan tool does not display engine data, go to next step.
  3. Turn ignition on with engine off. Using a DVOM, measure voltage between DLC power supply circuit and ground. See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6).
  4. Using a DVOM, measure voltage between DLC serial data output circuit and ground. See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 7).
  5. Using a test light connected to battery voltage, probe DLC ground circuits. See WIRING DIAGRAMS article. If test light illuminates on both circuits, go to step 10). If test light does not illuminate on either circuit, go to step 8).
  6. Repair open or short in DLC power supply circuit. After repairs, go to step 11).
  7. Repair open or short in DLC serial data output circuit. After repairs, go to step 11). If circuit is okay, go to step 9).
  8. Repair open(s) in DLC ground circuit(s). After repairs, go to step 11).
  9. Replace PCM. After repairs, go to step 11).
  10. Scan tool is faulty. Refer to scan tool manual for repairs. After repairs, go to next step.
  11. After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to DIAGNOSTIC AIDS.
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