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Home >> Cadillac >> 1997 >> Eldorado Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Engine Testing 4.6L >> On-Board Diagnostic (OBD) System Check >> DLC Diagnosis Or No Scan Tool Data
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DLC Diagnosis Or No Scan Tool Data

  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. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  . 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 the WIRING DIAGRAMS article. Voltage reading for both circuits should be 10 volts. If voltage readings are the same or higher for both circuits, go to step 7). If voltage readings are not the same or higher for both circuits, go to next step.
  4. Using DVOM, measure voltage between ground and DLC battery feed circuit. See the WIRING DIAGRAMS article. Voltage reading should be 10 volts. 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  . If scan tool does not display PCM data, go to next step.
  8. Install scan tool on 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. Reinstall scan tool on 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 Diagnostic Trouble Codes (DTCs). If DTCs are present, see the TESTS W/CODES article for related DTC diagnosis. 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. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  . 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  . If scan tool does not display PCM data, go to step 14).
  13. Replace faulty scan tool. After scan tool replacement, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  .
  14. Replace PCM. Perform PCM relearn procedures. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  .
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