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Home >> Oldsmobile >> 1997 >> Regency >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1651 - Fan 1 Relay Control Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING - 3.8L article. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. Turn ignition off. Disconnect PCM connectors. Turn ignition on. Using a DVOM, check voltage between engine ground and PCM harness connector fan 1 relay driver circuit. If voltage is 9-16 volts, go to next step. If voltage is not as specified, go to step 6).
  3. Using DVOM in 10-amp scale, check current between engine ground and fan 1 relay driver circuit for 2 minutes. If current remains .05-0.5 amp go to step 11). If current does not remain as specified, go to next step.
  4. Turn ignition off. Reconnect cooling fans. With PCM connectors still disconnected, disconnect fan 1 relay connector. Turn ignition on. Using DVOM, check voltage between engine ground and fan 1 relay driver circuit. If voltage is zero volts, go to step 10). If voltage is greater than zero volts, go to next step.
  5. Locate and repair short to voltage in fan 1 relay driver circuit. After repairs, go to step 16).
  6. Check fan 1 relay ignition feed fuse. If fuse is blown, go to next step. If fuse is okay, go to step 8).
  7. Locate and repair short to ground in fan 1 relay ignition feed circuit. Replace fuse. After repairs, go to step 16).
  8. Disconnect fan 1 relay connector. Turn ignition on. Check voltage between engine ground and fan 1 relay ignition feed circuit. If voltage is 9-16 volts, go to next step. If voltage is not as specified, go to step 13).
  9. Check fan 1 relay driver circuit for open or short to ground. If a problem is found, repair as necessary. After repairs, go to step 16). If no problem is found, go to next step.
  10. Check fan 1 relay driver and fan 1 relay ignition feed circuits for faulty connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to step 14).
  11. Turn ignition off. Reconnect PCM connectors. Disconnect fan 1 relay connector. Turn ignition on. Connect a test light between fan 1 relay harness connector fan 1 relay driver and ignition feed circuits. Using scan tool, cycle fan 1 relay on and off. If test light flashes on and off, go to DIAGNOSTIC AIDS. If test light does not flash on and off, go to next step.
  12. Check fan 1 relay driver circuit for faulty connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to step 15).
  13. Locate and repair open fan 1 relay ignition feed circuit. After repairs, and go to step 16).
  14. Replace fan 1 relay. After replacing relay, go to step 16).
  15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  16. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P1651. If scan tool displays DTC P1651 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1651 FAILED THIS IGN, repair is complete.
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