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Data Link Connector (DLC) Diagnosis

  1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, go to next step.
  2. Disconnect scan tool. Install scan tool to another vehicle of the same year and same systems. Turn ignition on with engine off. If scan tool communicates with PCM, go to next step. If scan tool does not communicate with PCM, go to step  4.
  3. Reconnect scan tool to original vehicle. Turn ignition on with engine off. If scan tool communicates with PCM, go to step  11. If scan tool does not communicate with PCM, go to next step.
  4. Scan tool may be faulty. Refer to scan tool instruction manual. After repairs, go to step  17.
  5. Turn ignition off. Disconnect PCM harness connectors. Using DVOM, measure resistance between DLC terminals No. 4 (ground circuit) and No. 2 (serial data class II circuit). See WIRING DIAGRAMS article. If resistance is less than 10 ohms, go to next step. If resistance is 10 ohms or greater, go to step  7.
  6. Disconnect Electronic Brake Control Module (EBCM) harness connector. Using DVOM, measure resistance between DLC terminals No. 4 (ground circuit) and No. 2 (serial data class II circuit). Disconnect other control modules connected to serial data class II circuit one at a time and re-measure resistance with each module disconnected. If resistance is greater than 10 ohms with any module disconnected, go to step  15. If resistance 10 ohms or less with any module disconnected, go to step  14.
  7. Turn ignition on with engine off. Using DVOM, measure voltage between DLC terminals No. 4 (ground circuit) and No. 2 (serial data class II circuit). See WIRING DIAGRAMS article. If voltage is less than one volt, go to next step. If voltage is one volt or greater, go to step  12.
  8. Turn ignition off. Using DVOM, measure resistance between DLC terminal No. 2 (serial data class II circuit) and PCM harness connector terminal C8 (serial data class II circuit). See WIRING DIAGRAMS article. If resistance is less than 10 ohms, go to next step. If resistance is 10 ohms or greater, go to step  13.
  9. Check for opens or shorts to ground in all power and ground circuits to PCM. Repair as necessary. After repairs, go to step  17. If all power and ground circuits are okay, go to next step.
  10. Check for poor connections at PCM. Repair as necessary. After repairs, go to step  17. If connections are okay, go to next step.
  11. Repair intermittent short or open in serial data class II circuit. After repairs, go to step  17.
  12. Repair short to voltage in serial data class II circuit. After repairs, go to step  17.
  13. Repair open in serial data class II circuit. After repairs, go to step  17.
  14. Repair short to ground in serial data class II circuit. After repairs, go to step  17.
  15. Replace control module that caused resistance to increase. After repairs, go to step  17.
  16. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
  17. Start engine and operate vehicle under conditions which original symptom was noted. If system does not operate properly, go to step  2. If system operates properly, go to ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK .
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