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HOMESERVICE MANUALSCHEVROLET1999CUTAWAY 7.4 JREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P1537-U1193DTC P1641DTC P1641: A/C RELAY CONTROL CIRCUIT (3.1L "N" BODY & 3.4L "U" SERIES)DIAGNOSTIC PROCEDURES
1999 Chevrolet Cutaway 7.4 J

Diagnostic Procedures

1999 Chevrolet Cutaway 7.4 JSECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, 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. Using DVOM, set DVOM 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 reading is zero volts, go to step  10. If voltage reading 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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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.