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Home >> Chevrolet >> 1998 >> Venture Base, Van Cargo Extended >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 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 , then go to next step.
  2. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between ground and A/C relay driver circuit terminal at PCM connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6).
  3. Set amp meter to 10-amp range. Measure current between ground and MIL driver circuit terminal at PCM connector. Monitor reading for a minimum of 2 minutes. If current is 0.1-1.5 amps, go to step 11). If current is not 0.1-1.5 amps, go to next step.
  4. Turn ignition off. Disconnect instrument cluster connector. Turn ignition on. Using DVOM, check voltage between ground and A/C relay driver circuit terminal at PCM connector. 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 relay driver circuit. After repairs, go to step 15).
  6. Remove and inspect fuse for A/C 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 relay. After repairs, go to step 15).
  8. Disconnect instrument cluster connector. Turn ignition on. Check voltage between ground and ignition feed circuit terminal for A/C relay. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13).
  9. Check for an open or short to ground in A/C relay driver circuit. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to next step.
  10. Check A/C relay driver circuit and ignition feed circuit for poor terminal connection at PCM connector. Repair as necessary. After repairs, go to step 15). If connections are okay, go to step 14).
  11. Turn ignition off. Reconnect PCM connector. Disconnect A/C relay connector. Turn ignition on. Connect a test light between affected output driver circuit and ignition feed circuit terminals at A/C relay harness connector. Using scan tool, select OUTPUTS TEST function and cycle A/C relay on and off. If test light flashes, see DIAGNOSTIC AIDS. If test light does not flash, go to next step.
  12. Check A/C relay driver circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 15). If connection is okay, go to step 14).
  13. Locate and repair open in ignition feed circuit to A/C relay. After repairs, go to step 15).
  14. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  15. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1641 until DTC P1641 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.
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