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DLC Diagnosis Or No Scan Tool Data: 4.6L

  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. See appropriate wiring diagram in WIRING DIAGRAMS article. 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 blown 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 on-board diagnostics. If on-board diagnostics is entered, go to next step. If on-board diagnostics cannot be entered, diagnose vehicle computer system.
  10. Using on-board diagnostics display, check all control modules for DTCs. If DTCs are present, diagnose DTCs. See DIAGNOSTIC TESTS in appropriate TESTS W/CODES article. If DTCs are not present, go to next step.
  11. Check for open in class 2 serial data circuit between DLC and PCM. Repair as necessary. If circuit is okay, go to next step.
  12. Check DLC terminal connection. Repair as necessary. Exit on-board diagnostics. Reconnect scan tool. 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 step  14.
  13. Replace faulty scan tool.
  14. Replace PCM. Perform PCM relearn procedures.
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