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DLC Diagnosis Or No Scan Tool Data: 4.0L

NOTE: Perform On-Board Diagnostic (OBD) system check after completing any repairs. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK .
  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. Check all PCM power and ground connections and circuits. Repair as necessary. If connections and circuits are okay, go to next step.
  3. Ensure battery is fully charged. Using DVOM, measure voltage between DLC battery feed circuit and DLC ground circuits. See appropriate wiring diagram in WIRING DIAGRAMS article. Voltage reading for both circuits should be 10 volts or greater. If voltage is as specified, go to step  7. If voltage is not as specified, go to next step.
  4. Using DVOM, measure voltage between ground and DLC battery feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Voltage reading should be 10 volts or greater. If voltage is as specified, go to next step. If voltage is not as specified, go to step  6.
  5. Repair open in DLC ground circuit that had low or no voltage. After repairs, go to step  7.
  6. Repair open or short to ground in DLC battery feed circuit. Replace open fuse as necessary. After repairs, go to next step.
  7. Turn ignition on. If scan tool displays PCM data, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If scan tool does not display PCM data, go to next step.
  8. Connect scan tool to another vehicle and check for proper operation. If scan tool operates properly, go to next step. If scan tool does not operate properly, go to step  13.
  9. Reconnect scan tool to original vehicle and enter fluid life information. Turn ignition off and wait 30 seconds. Disconnect PCM harness connector C1. Using DVOM, measure resistance of class 2 serial data circuit between PCM and DLC. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is greater than 5 ohms, go to step  11. If resistance is not greater than 5 ohms, go to next step.
  10. Disconnect Remote Accessory Control (RAC) module harness connector. Using DVOM, measure resistance of DLC class 2 serial data circuit to ground. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is less than 10,000 ohms, go to step  12. If resistance is 10,000 ohms or greater, go to step  14.
  11. Repair open in class 2 serial data circuit.
  12. Repair short to ground in class 2 serial data circuit.
  13. Replace faulty scan tool.
  14. Reconnect PCM harness connectors. Check for PCM data with RAC module disconnected. If scan tool displays PCM data, go to step  17. If scan tool does not display PCM data, go to next step.
  15. Check connections at PCM harness connector C1. Repair as necessary. If connections are okay, go to next step.
  16. Replace PCM. Perform PCM relearn procedures.
  17. Replace RAC module.
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