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Home >> Oldsmobile >> 1998 >> Regency >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1641 - A/C Relay Control Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, 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 A/C compressor control relay control circuit. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6).
  3. Using DVOM in 10-amp scale, check current between engine ground and A/C compressor control relay control circuit for 2 minutes. If current remains at 0.05-0.50 amp, go to step 11). If current does not remain at 0.05-0.50 amp, go to next step.
  4. Turn ignition off. Disconnect PCM harness connector and A/C compressor control relay connector. Turn ignition on. Using DVOM, check voltage between engine ground and A/C relay control driver circuit. If voltage is zero volts, go to step 10). If voltage is not zero volts, go to next step.
  5. Locate and repair short to voltage in A/C compressor control relay control circuit. After repairs, go to step 16).
  6. Check ignition feed fuse for A/C compressor control relay. If fuse is blown, go to next step. If fuse is okay, go to step 8).
  7. Locate and repair short to ground in ignition feed circuit for A/C compressor control relay. Replace fuse. After repairs, go to step 16).
  8. Disconnect A/C compressor control relay. Turn ignition on. Check voltage between engine ground and A/C compressor control relay ignition feed circuit. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13).
  9. Check A/C compressor control relay circuit for open or short to ground. If a problem is found, repair as necessary. After repairs, go to step 16). If circuit is okay, go to next step.
  10. Check A/C compressor control relay circuits for faulty connection at PCM or faulty connection at relay connector. Repair as necessary. After repairs, go to step 16). If connection is okay, go to step 14).
  11. Turn ignition off. Reconnect A/C compressor clutch and PCM connectors. Disconnect A/C compressor control relay connector. Turn ignition on. Connect a test light between A/C compressor control relay connector and ignition feed circuits at relay connector. Using scan tool, cycle A/C compressor control relay on and off. If test light flashes on and off, see DIAGNOSTIC AIDS. If test light does not flash on and off, go to next step.
  12. Check A/C compressor control relay control circuit for faulty connection at PCM. Repair as necessary. After repairs, go to step 16). If connection is okay, go to step 15).
  13. Locate and repair open ignition feed circuit to A/C compressor control relay. After repairs, go to step 16).
  14. Replace A/C compressor control 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 P1641. If scan tool displays DTC P1641 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1641 FAILED THIS IGN, repair is complete.
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