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HVAC System - Compressor Clutch Controls: Diagnosis Chevrolet Venture I

A/c Compressor ~11560 words

A/C CLUTCH CIRCUIT DIAGNOSIS (CARS)

To help save diagnostic time, ALWAYS check for blown fuses or fusible links before proceeding with diagnosis. If fuses are blown, locate and repair short circuit before replacing fuses.

Ensure all related relay and wire harness connections are clean and tight. Repair as necessary. See WIRING DIAGRAMS .

Note. Vehicles may be equipped with a PCM using an Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing PCM, the new PCM must be programmed.

Diagnostic System Check

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Body Control Module (BCM) and Powertrain Control Module (PCM). If communication with both modules is established, go to next step. If communication with both modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTC. If DTCs are displayed, go to next step. If no DTCs are displayed, see «DIAGNOSIS»(ref-96385-S25679310302001041000000) .
  4. If scan tool displays any DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

Diagnosis

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S40840348812001050800000) . If diagnostic system check has been performed, go to next step.
  2. Install scan tool. Check for any DTCs that may be set. If DTC P0530 or U1016 are set, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 5 .
  4. Remove A/C clutch relay. If A/C compressor clutch disengages, go to step 6 . If A/C compressor clutch does not disengage, go to step 7 .
  5. Start engine and allow it to reach normal operating temperature. Cycle A/C on and off at control panel. If A/C compressor clutch cycles on and off, go to step 8 . If A/C compressor clutch does not cycle on and off, go to step 9 .
  6. Using a test light connected to battery voltage, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at A/C clutch relay connector. See «WIRING DIAGRAMS»(ref-96385-S06134121212001050800000) . If test light comes on, go to step 20 . If test light does not come on, go to step 30 .
  7. Disconnect A/C compressor clutch harness connector. If A/C compressor clutch disengages, go to step 21 . If A/C compressor clutch does not disengage, go to step 32 .
  8. Turn ignition switch to OFF position. Install A/C manifold gauge set. Compare high-side pressure reading on gauge with scan tool reading. If readings are within 20 psi (1.4 kg/cm 2 ) of each other, go to step 36 . If readings are not as specified, go to step 10 .
  9. While observing scan tool, turn A/C on, then off. If scan tool indicates A/C was requested, then not requested, go to step 11 . If operation is not as specified, go to step 12 .
  10. Disconnect A/C refrigerant pressure sensor electrical connector. Connect DVOM between battery voltage and A/C refrigerant pressure sensor ground circuit (Black wire). If DVOM reads battery voltage, go to step 31 . If DVOM does not read battery voltage, go to step 22 .
  11. Turn engine off, leaving ignition switch in ON position. If A/C high side value is 40-430 psi (2.8-30.2 kg/cm 2 ), go to step 13 . If A/C high side value is not 40-430 psi (2.8-30.2 kg/cm 2 ) go to step 14 .
  12. Connect test light between ground and A/C selector switch input circuit (Light Green/Black wire) to instrument cluster. Cycle A/C selector switch on and off. If test light turns on and off when A/C selector switch is cycled, go to step 34 . If test light does not turn on and off when A/C selector switch is cycled, go to step 23 .
  13. Remove A/C relay. Using a test light connected to ground, probe ignition feed circuit (Pink wire) and battery feed circuit (Orange wire). If test light is on for both circuits, go to step 15 . If test light is off for both circuits, go to step 24 .
  14. Install an A/C manifold gauge set. Observe A/C high side pressure on scan tool and manifold gauge set. If A/C high side pressure is within 20 psi (1.4 kg/cm 2 ) of each other, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S40840348812001050800000) . If A/C high side pressure is not within 20 psi (1.4 kg/cm 2 ) of each other, go to step 31 .
  15. Connect a fused jumper between A/C relay ignition feed terminal No. 85 (Pink wire) and compressor clutch feed terminal No. 87 (Dark Green wire). If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 17 .
  16. Remove fused jumper wire. Start engine. Ensure A/C is selected on, then command A/C compressor clutch relay on using scan tool. Using a test light connected to battery voltage, probe A/C compressor clutch relay control terminal No. 86 (Dark Green/White wire). If test light is on, go to step 30 . If test light is off, go to step 18 .
  17. Disconnect A/C compressor clutch electrical connector. Leave fused jumper connected. Using a test light connected to ground, probe A/C compressor clutch ignition feed circuit (Dark Green wire). If test light is on, go to step 19 . If test light is off, go to step 26 .
  18. Turn ignition switch to ON position, with engine OFF. Using a test light connected to ground, probe compressor clutch relay control terminal No. 86 (Dark Green/White wire). If test light is on, go to step 27 . If test light is off, go to step 28 .
  19. Using a test light connected to battery voltage, probe A/C compressor clutch ground circuit (Black wire) at A/C compressor clutch connector. If test light is on, go to step 33 . If test light is off, go to step 29 .
  20. Check A/C compressor clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 35 .
  21. Repair short to battery voltage in A/C compressor clutch ignition feed circuit (Dark Green wire). After repairs, go to step 36 .
  22. Check A/C refrigerant pressure sensor ground (Black wire) for open or poor connections. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 35 .
  23. Repair signal from A/C selector switch. After repairs, go to step 36 .
  24. If test light was not on at A/C relay battery feed terminal No. 30 or ignition feed terminal No. 85, check short to ground in A/C compressor clutch ignition feed circuit (Dark Green wire), A/C compressor clutch diode, battery feed circuit (Orange wire) and ignition feed circuit (Pink wire). If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to next step.
  25. Turn ignition switch to OFF position. Check for open in A/C compressor clutch relay battery feed circuit (Orange wire) and ignition feed circuit (Pink wire). If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 30 .
  26. Turn ignition switch to OFF position. Repair open in A/C compressor clutch ignition feed circuit (Dark Green wire). After repairs, go to step 36 .
  27. Check A/C compressor clutch relay control circuit (Dark Green/White wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 35 .
  28. Check A/C compressor clutch relay control circuit (Dark Green/White wire) for open or poor connections. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 35 .
  29. Repair open or poor connections in A/C compressor clutch ground circuit (Black wire). After repairs, go to step 36 .
  30. Turn ignition switch to OFF position. Check for poor connections at A/C relay. If connections are okay, replace A/C compressor clutch relay. After repairs, go to step 36 .
  31. Check for poor connections at A/C refrigerant pressure sensor. If connections are okay, replace A/C refrigerant pressure sensor. After repairs, go to step 36 .
  32. Replace malfunctioning A/C compressor clutch assembly. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 36 .
  33. Turn ignition switch to OFF position. Check for poor connections at A/C compressor clutch coil. If connections are okay, replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 36 .
  34. See SELF-DIAGNOSTIC SYSTEM in appropriate ANALOG INSTRUMENT PANELS article. After repairs, go to step 36 .
  35. Turn ignition switch to OFF position. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  36. Start engine. Idle engine. Cycle A/C selector switch on and off. If A/C compressor clutch cycles on and off, system is okay.

Diagnostic Aids

If DTCs P0530 or U1060 are set, diagnose them before proceeding. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If problem is insufficient cooling, check cooling fans for proper operation. See ELECTRIC COOLING FANS - ALL MODELS article. If cooling fans operate correctly, diagnose manual A/C-heater system. See MANUAL A/C-HEATER SYSTEMS - CAVALIER & SUNFIRE article.

An A/C refrigerant pressure less than 43 psi (3.0 kg/cm 2 ), or greater than 428 psi (30.1 kg/cm 2 ), will cause PCM to disable compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side pressure for 2 minutes. If pressure goes out of range, diagnose manual A/C-heater system.

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S09111073862001041200000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S37862045142001041200000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S09255976082001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S40064889772001041300000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

If DTCs P0530, U1016 or U1064 are set, diagnose them before proceeding. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If problem is insufficient cooling, check cooling fans for proper operation. See ELECTRIC COOLING FANS - ALL MODELS article. If cooling fans operate correctly, diagnose manual A/C-heater system. See appropriate MANUAL A/C-HEATER SYSTEMS article.

An A/C refrigerant pressure less than 43 psi (3.0 kg/cm 2 ), or greater than 428 psi (30.1 kg/cm 2 ), will cause PCM to disable A/C compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side system pressure for 2 minutes. If pressure goes out of range, diagnose manual A/C-heater system. See appropriate MANUAL A/C-HEATER SYSTEMS article.

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Instrument Panel Cluster (IPC), Body Control Module (BCM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTC. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S30588214342001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S36673822652001041000000) .
  4. If scan tool displays any DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

An intermittent condition may be caused by corrosion, misrouted wiring harness, rubbed through wire insulation, or a wire broken inside insulation. Perform visual inspection and check for continuity along suspect circuits. Repair as necessary.

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with HVAC control module, Body Control Module (BCM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTC. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE (AUTOMATIC A/C)»(ref-96385-S38606006872001041000000) , «COMPRESSOR CLUTCH DOES NOT ENGAGE (MANUAL A/C)»(ref-96385-S16143482542001041700000) , «COMPRESSOR CLUTCH DOES NOT DISENGAGE (AUTOMATIC A/C)»(ref-96385-S32787971752001041700000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE (MANUAL A/C)»(ref-96385-S03447831512001041700000) .
  4. If scan tool displays any DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

An intermittent condition may be caused by corrosion, misrouted wiring harness, rubbed through wire insulation or a wire broken inside insulation. Perform visual inspection and check for continuity along suspect circuits. Repair as necessary.

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S26564462282001041700000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S12365760762001041700000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Body Control Module (BCM) and Powertrain Control Module (PCM). If communication with BCM and PCM is established, go to next step. If communication with BCM or PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for BCM and PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «DIAGNOSIS»(ref-96385-S42142847312001041000000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S40657163522001041800000) . If diagnostic system check has been performed, go to next step.
  2. Turn A/C selector switch to OFF position. Turn ignition switch to ON position, with engine off. Listen for engagement of A/C clutch. If A/C clutch engages, go to step 17 . If A/C clutch does not engage, go to next step.
  3. Start engine. Select DEFROST or MAX mode on HVAC control. Observe A/C compressor. If A/C compressor clutch engages, see «DIAGNOSTIC AIDS»(ref-96385-S14831060662001041000000) . If A/C clutch does not engage, go to next step.
  4. With DEFROST or MAX mode selected, monitor A/C REQUEST display on scan tool in ENGINE data list. If A/C REQUEST displays YES, go to step 8 . If A/C REQUEST does not display YES, go to next step.
  5. Turn ignition switch to OFF position. Disconnect PCM. Turn ignition switch to ON position. With DEFROST or MAX mode selected, measure voltage between A/C request circuit (Light Green wire) at PCM harness connector and ground. If battery voltage is present, go to step 7 . If battery voltage is not present, go to next step.
  6. Check A/C request circuit (Light Green wire) for open, shorted to ground or poor connections. If problem was found, repair as necessary. After repair, go to step 28 . If problem was found, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S40657163522001041800000) .
  7. Check A/C request circuit (Light Green wire) for poor connection at PCM. If problem was found, repair as necessary. After repairs, go to step 28 . If problem was not found, go to step 26 .
  8. Observe A/C REFRIGERANT PRESSURE display on scan tool. If A/C pressure is 36 - 440 psi (2.5-31 kg/cm 2 ), go to step 11 . If A/C pressure is not 36-440 psi (2.5-31 kg/cm 2 ), go to next step.
  9. Connect Manifold Gauge Set (J 39183-C R-134a). Observe high side refrigerant pressure on gauge. If high side refrigerant pressure is 36-440 psi (2.5-31 kg/cm 2 ), go to next step. If high side refrigerant pressure is not 36-440 psi (2.5-31 kg/cm 2 ), see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S40657163522001041800000) .
  10. Turn ignition switch to OFF position. Disconnect A/C Pressure sensor. Turn ignition switch to ON position. View A/C HIGHSIDE display on scan tool in ENGINE data list. If scan tool displays A/C HIGHSIDE pressure at zero psi, go to step 27 . If scan tool does not display A/C HIGHSIDE pressure at zero psi, go to step 26 .
  11. Disconnect A/C relay connector. Using test light connected to ground, probe ignition feed circuits (Pink wires) at A/C relay connector. If test light is on, go to next step. If test light is off, go to step 22 .
  12. Connect fused jumper between ignition feed circuit (Pink wire) and A/C compressor clutch control circuit (Dark Green wire) at A/C relay connector. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 14 .
  13. Check A/C relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 28 . If problem was not found, go to step 23 .
  14. Disconnect A/C compressor clutch connector (leave ignition control circuit and A/C compressor clutch control circuit jumpered at A/C relay connector). Connect test light between A/C compressor clutch feed circuit (Dark Green wire) and compressor ground circuit (Black wire). If test light is on, go to next step. If test light is off, go to step 16 .
  15. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 28 . If problem was not found, go to step 24 .
  16. Check A/C compressor clutch control circuit (Dark Green/White wire) for open or short to ground. If problem was found, repair as necessary. After repairs, go to step 28 . If problem was not found, go to step 25 .
  17. Turn ignition switch to ON position. Turn A/C off. Observe A/C REQUEST display on scan tool. If A/C REQUEST displays YES, go to next step. If A/C REQUEST does not display YES, go to step 20 .
  18. Turn ignition switch to OFF position. Disconnect PCM. Turn ignition to ON position. Turn A/C off. Using DVOM, measure voltage between A/C request circuit (Light Green wire) at PCM connector and ground. If battery voltage is present, go to next step. If battery voltage is not present, go to step 26 .
  19. Turn ignition switch to OFF position. Disconnect A/C control head. Turn ignition switch to ON position. Check A/C request circuit (Light Green wire) for short to battery voltage. If problem was found, repair as necessary. After repairs, go to step 28 . If problem was not found, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S40657163522001041800000) .
  20. Disconnect A/C relay. Start vehicle and observe A/C compressor. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 23 .
  21. Repair short to voltage in A/C compressor clutch control circuit (Dark Green/White wire). After repairs, go to step 28 .
  22. Repair open or short to ground in ignition feed circuit (Pink wire) to A/C compressor relay. After repairs, go to step 28 .
  23. Replace A/C compressor relay. After repairs, go to step 28 .
  24. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 28 .
  25. Repair open in A/C compressor clutch ground circuit (Black wire). After repairs, go to step 28 .
  26. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to step 28 .
  27. Replace A/C refrigerant pressure sensor. After repairs, go to next step.
  28. Start engine. Turn A/C selector switch to ON position. Listen for engagement of A/C clutch. If A/C clutch engages, system is okay.

An intermittent condition may be caused by corrosion, misrouted wiring harness, rubbed through wire insulation or a wire broken inside insulation. Perform visual inspection and check for continuity along suspect circuits. Repair as necessary. If circuits are okay, check conditions listed under DESCRIPTION .

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S21443843692001041800000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S10118194552001041800000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Body Control Module (BCM), Dash Integration Module (DIM), Instrument Panel Module (IPM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S07612557032001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S12676163252001041900000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

An intermittent condition may be caused by corrosion, misrouted wiring harness, rubbed through wire insulation or a wire broken inside insulation. Perform visual inspection and check for continuity along suspect circuits. Repair as necessary.

Diagnostic System Check (Automatic A/C)

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Dash Integration Module (DIM), Instrument Panel Module (IPM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT DISENGAGE (AUTOMATIC A/C)»(ref-96385-S03475008932001042000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE (AUTOMATIC A/C)»(ref-96385-S03475008932001042000000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

Diagnostic System Check (Manual A/C)

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with A/C-heater control module, Dash Integration Module (DIM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE (MANUAL A/C)»(ref-96385-S32771238452001042000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE (MANUAL A/C)»(ref-96385-S15860352222001042000000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with A/C-heater control module, Body Control Module (BCM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S17723172252001042000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S34841053182001042000000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S35018633322001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S21455717672001042300000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

Check for poor harness connections at PCM and A/C control head. Inspect for corrosion, backed-out terminal pins, and broken wires inside insulation. Check for damaged wire harness. If harness and connections are okay, disconnect PCM harness connectors. Connect a DVOM between ground and A/C clutch relay control circuit at PCM harness connector. Turn ignition switch to ON position. Observe DVOM while wiggling harness and connectors. A change in voltage indicates location of fault.

An A/C refrigerant pressure less than 35 psi (2.5 kg/cm 2 ), or greater than 414 psi (29.1 kg/cm 2 ) will cause PCM to disable A/C compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side system pressure for 2 minutes. If pressure goes out of range, diagnose A/C-heater system. See MANUAL A/C-HEATER SYSTEMS - CAMARO & FIREBIRD article.

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Dash Integration module (DIM), Instrument Panel Module (IPM), Powertrain Control Module (PCM) and rear climate control. If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S03851535902001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S34268621292001042400000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with HVAC control module, Body Control Module (BCM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S06124822872001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S09337832202001042400000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with HVAC control module, Body Control Module (BCM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE (AUTOMATIC A/C)»(ref-96385-S08945995122001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE (AUTOMATIC A/C)»(ref-96385-S06927812352001042500000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE (MANUAL A/C)»(ref-96385-S00522929202001042500000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE (MANUAL A/C)»(ref-96385-S40782146052001042500000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

A/C CLUTCH CIRCUIT DIAGNOSIS (LIGHT TRUCKS & VANS)

To save diagnostic time, ALWAYS check for blown fuses or fusible links before proceeding with diagnosis. If fuses are blown, locate and repair short circuit before replacing fuses. Ensure all related relay and wire harness connections are clean and tight. Repair as necessary. See WIRING DIAGRAMS .

Note. Vehicles may be equipped with a PCM using an Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing PCM, the new PCM must be programmed.

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM) on 2001 vehicles or HVAC control module on 2000 models. On all models, if communication with module is established, go to next step. If communication with module is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S12382334652001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S38503781942001042700000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S16717615462001042700000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S32371855712001042700000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Body Control Module (BCM) and Powertrain Control Module (PCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S16874916722001041000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S23629992092001043000000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

Check for poor harness connections at PCM and A/C-heater control panel. Inspect for corrosion, backed-out terminal pins, and broken wires inside insulation. Check for damaged wire harness. If harness and connections are okay, disconnect PCM harness connectors. Connect a DVOM between ground and A/C clutch relay control circuit at PCM harness connector. Turn ignition switch to ON position. Observe DVOM while wiggling harness and connectors. A change in voltage indicates location of fault.

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S31532691422001043000000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S04135053432001043000000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with HVAC control module, Body Control Module (BCM) and Powertrain Control Module (PCM)/Vehicle Control Module (VCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S05575600082001050100000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S25857285952001050100000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM)/Vehicle Control Module (VCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S35512105032001050200000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S19036738512001050200000) .
  4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. This diagnostic test assumes the following: A/C system is adequately charged. This table only diagnoses control of A/C compressor clutch. A/C compressor has no mechanical failures. Engine coolant temperature is more than 140°F (60°C), but less than 250°F (121°C). HVAC control module is functioning. Start and idle engine. Turn off HVAC controls. If A/C compressor clutch engaged, go to step 4 . If A/C compressor clutch did not engage, go to next step.
  3. Start engine. Idle engine until normal operating temperature is reached. Leave engine at normal idle. Turn A/C on. If A/C clutch engage within 60 seconds, see «DIAGNOSTIC AIDS»(ref-96385-S27928682612001041000000) . If A/C clutch does not engage within 60 seconds, go to step 7 .
  4. Disconnect A/C clutch relay from underhood electrical center. If A/C compressor clutch stays engaged, go to next step. If A/C compressor clutch does not stay engaged, go to step 6 .
  5. Check for short to voltage in Dark Green wire between A/C clutch relay and A/C compressor clutch. If problem was found, go to step 33 . If problem was not found, go to step 17 .
  6. Using test light connected to battery voltage, probe A/C clutch relay control circuit (Dark Green/White wire) at underhood electrical center. If test light is on, go to step 24 . If test light is off, go to step 29 .
  7. Install scan tool. Start engine. Turn A/C on. Monitor A/C REQUEST in scan tool data list. A/C request should display YES. If scan tool displays YES, go to next step. If scan tool does not display YES, go to step 18 .
  8. Monitor A/C EVAPORATOR SWITCH with scan tool. Turn A/C on. If scan tool indicates switch is CLOSED, go to step 12 . If scan tool does not indicate switch is CLOSED, go to next step.
  9. Disconnect A/C evaporator cycling cutoff switch connector. Turn ignition switch to ON position, with engine off. Using fused jumper, connect Dark Green wire at A/C evaporator cycling cutoff switch connector to ground. If scan tool indicates switch is CLOSED, go to next step. If scan tool does not indicate switch is CLOSED, go to step 31 .
  10. Using test light connected to battery voltage, probe ground circuit (Black wire) of A/C evaporator cycling cutoff switch connector. If test light is on, go to next step. If test light is off, go to step 33 .
  11. Replace A/C high pressure cutoff switch. After repairs, go to step 35 .
  12. Turn engine off. Disconnect A/C compressor clutch harness connector. Start engine. Turn A/C on. Using test light connected to ground, probe A/C clutch voltage supply circuit (Dark Green wire) at A/C compressor clutch harness connector. If test light is on, go to next step. If test light is off, go to step 20 .
  13. Using test light connected to ground, probe A/C clutch ground circuit (Black wire) at A/C clutch connector. If test light is on, go to step 15 . If test light is off, go to next step.
  14. Repair A/C clutch ground circuit (Black wire). After repairs, go to step 35 .
  15. Check A/C compressor clutch connector for poor connections. If problem was found, go to next step. If problem was not found, go to step 17 .
  16. Repair A/C compressor clutch connector. After repairs, go to step 35 .
  17. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 35 .
  18. Turn ignition switch to OFF position. Disconnect VCM connector C3. Turn ignition switch to ON position, with engine off. Turn A/C on. Using test light connected to ground, probe the VCM connector C3 terminal No. 25 (Dark Green/White wire). If test light is on, go to step 32 . If test light is off, go to next step.
  19. Check for open in A/C request signal circuit (Light Blue wire and Dark Green/White wire) between HVAC control module and VCM. If problem was found, go to step 33 . If problem was not found, see TESTING in appropriate MANUAL A/C-HEATER SYSTEMS article.
  20. Reconnect A/C clutch connector. Install scan tool. Turn ignition switch to ON position, with engine off. Using scan tool, command A/C relay on. If A/C relay clicks, go to step 26 . If A/C relay does not click, go to next step.
  21. Disconnect A/C relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe ignition voltage circuit (Pink wire on 7.4L) at A/C relay connector. If test light is on, go to step 23 . If test light is off, go to next step.
  22. Repair open in A/C relay ignition voltage circuit (Pink wire on 7.4L). If fuse is blown, repair short to ground in A/C relay ignition voltage circuit. After repairs, go to step 35 .
  23. Using test light connected to battery voltage, probe A/C relay control circuit (Dark Green/White wire) at A/C relay connector. Using scan tool, command A/C relay on. If test light is on, go to step 29 . If test light is off, go to next step.
  24. Check for open, short to voltage or short to ground in A/C relay control circuit (Dark Green/White wire) between the underhood fuse block and VCM connector C3. If problem was found, go to next step. If problem was not found, go to step 32 .
  25. Repair Dark Green/White wire between underhood fuse block and VCM connector C3. After repairs, go to step 35 .
  26. Remove A/C compressor clutch relay. Using test light connected to ground, probe battery voltage circuit (Orange wire on 7.4L) at A/C compressor clutch relay connector. If test light is on, go to step 28 . If test light is off, go to next step.
  27. Repair open in A/C relay battery voltage feed circuit (Pink wire on 7.4L). If fuse is blown, repair short to ground in A/C relay battery voltage circuit. After repairs, go to step 35 .
  28. Turn ignition switch to ON position, with engine off. Using fused jumper, connect A/C relay battery voltage feed circuit to A/C clutch voltage supply circuit (Dark Green wire) at A/C compressor clutch relay connector. If A/C clutch engages, go to next step. If A/C clutch does not engage, go to step 30 .
  29. Replace A/C compressor clutch relay. After repairs, go to step 35 .
  30. Repair open or short to ground in A/C compressor clutch control circuit (Dark Green/White wire). After repairs, go to step 35 .
  31. Check for open in A/C cycling signal circuit (Dark Green wire). If problem was found, go to step 33 . If problem was not found, go to next step.
  32. Check VCM connectors for poor connections. If problem was found, go to next step. If problem was not found, go to step 34 .
  33. Repair circuit as necessary. After repairs, go to step 35 .
  34. Replace VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  35. Start engine. Idle engine until normal operating temperature is reached. Leave engine at normal idle. Turn A/C on. A/C clutch should engage within 60 seconds. Using scan tool, check for DTCs. If DTCs are not present, system is okay.

Intermittent conditions can be caused by poor connections, rubbed wire through insulation or a broken wire within the insulation. Check circuits thoroughly. For additional information, see appropriate MANUAL A/C-HEATER SYSTEMS article.

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. This diagnostic procedure only diagnoses the A/C compressor clutch circuit. This procedure assumes the following conditions are true: A/C system is fully charged. A/C compressor has no mechanical failures. Engine coolant temperature is greater than 140°F (60°C), but less than 250°F (121°C). HVAC control module is functioning normally. Start engine and turn HVAC controls to off position. If A/C compressor clutch is engaged, go to step 12 . If A/C compressor clutch is not engaged, go to next step.
  3. Select any A/C position on HVAC control panel. Set blower switch to high. If A/C compressor clutch engages, system is operating properly at this time. If A/C compressor clutch is not engaged, go to next step.
  4. Check condition of both A/C and IGN E fuses (10 amp). If both fuses are okay, go to next step. If one or more fuses are blown, go to step 28 .
  5. Connect scan tool and monitor A/C request signal. If scan tool displays A/C request as YES, go to next step. If scan tool does not display A/C request as YES, go to step 20 .
  6. Monitor A/C compressor cycling switch signal with scan tool. If scan tool displays A/C cycling switch as closed, go to next step. If scan tool does not display A/C cycling switch as closed, go to step 24 .
  7. Turn ignition switch to OFF position. Disconnect A/C clutch relay. Turn ignition switch on, engine off. Using test light connected to battery voltage, probe A/C clutch relay control circuit (Dark Green/White wire). See «WIRING DIAGRAMS»(ref-96385-S06134121212001050800000) . Using scan tool, command A/C clutch relay on and off. If test light turns on and off, go to next step. If test light does not turn on and off, go to step 31 .
  8. Using test light connected to ground, probe both A/C relay battery voltage supply circuits. If test light comes on at both terminals, go to next step. If test light does not come on at both terminals, go to step 32 .
  9. Connect a fused jumper between battery voltage circuit and A/C compressor clutch circuit (Dark Green wire). If A/C compressor clutch engages, go to step 34 . If A/C compressor clutch does not engage, go to next step.
  10. Using fused jumper connected, raise and support vehicle. Disconnect A/C compressor clutch connector. Using test light connected to ground, probe A/C compressor clutch connector feed from relay terminal (Dark Green wire). If test light comes on, go to next step. If test light does not come on, go to step 33 .
  11. Connect a test light between terminals of A/C compressor clutch connector. If test light comes on, go to step 35 . If test light does not come on, go to step 36 .
  12. Monitor A/C request signal on scan tool. If scan tool indicates A/C request as YES, go to next step. If scan tool indicates A/C request as NO, go to step 16 .
  13. Disconnect A/C high pressure cut-out switch located on rear of compressor. If scan tool indicates A/C request as YES, go to next step. If scan tool indicates A/C request as NO, diagnose A/C-heater system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.
  14. Turn ignition switch to OFF position. Disconnect PCM connector C2. Turn ignition switch to ON position. Use a DVOM to measure voltage between PCM connector C2 A/C request terminal (Dark Green/White wire) and ground. If any voltage reading is indicated, go to step 37 . If no voltage reading is indicated, go to next step.
  15. Turn ignition switch to OFF position. Use a DVOM to measure resistance between A/C request terminal (Dark Green/White wire) and all other terminals at connector C2. If reading is 0-2 ohms at any terminal, go to step 38 . If reading is not 0-2 ohms at any terminal, go to step 55 .
  16. Disconnect A/C clutch relay. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 39 .
  17. Using test light connected to battery voltage, probe A/C clutch relay control circuit (Dark Green/White wire) at relay connector. If test light comes on, go to next step. If test light does not come on, go to step 40 .
  18. Turn ignition switch to OFF position. Disconnect PCM connector C2. Using test light connected to battery voltage, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at PCM connector C2. If test light comes on, go to step 41 . If test light does not come on, go to next step.
  19. Using DVOM, measure resistance between A/C clutch relay control circuit terminal (Dark Green/White wire) and all other terminals at connector C2. If reading is 0-2 ohms at any terminal, go to step 42 . If reading is not 0-2 ohms at any terminal, go to step 55 .
  20. Turn engine off. Disconnect A/C high pressure cut-out switch located on rear of compressor. Turn ignition switch to ON position. Using DVOM, measure voltage between ground and A/C request circuit (Dark Green/White wire) on HVAC module side. If battery voltage is indicated, go to next step. If battery voltage is not indicated, diagnose A/C-heater system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.
  21. Connect a fused jumper wire between A/C high pressure cut-out switch connector terminals. Start engine and monitor A/C REQUEST on scan tool. If scan tool indicates A/C REQUEST as YES, go to step 43 . If scan tool does not indicate A/C REQUEST as YES, go to next step.
  22. Turn ignition switch to OFF position. Disconnect PCM connector C2. Using DVOM, check for continuity of A/C request signal circuit between PCM and A/C high pressure cut-out switch (Dark Green/White wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 45 .
  23. Using DVOM, check continuity of A/C request signal circuit to ground. If continuity is indicated, go to step 46 . If continuity is not indicated, go to step 54 .
  24. Turn engine off. Disconnect A/C compressor cycling switch connector to the accumulator. Turn ignition switch to ON position. Using DVOM, measure voltage between battery ground and A/C compressor cycling switch signal circuit (Dark Green wire). If battery voltage is indicated, go to next step. If battery voltage is not indicated, go to step 26 .
  25. Connect a fused jumper wire between A/C compressor cycling switch connector terminals. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH as CLOSED, go to step 47 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH as CLOSED, go to step 49 .
  26. Turn ignition switch to OFF position. Disconnect PCM connector C2. Using DVOM, check continuity of A/C compressor cycling switch circuit between PCM and cycling switch (Dark Green wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 50 .
  27. Using DVOM, check continuity between A/C compressor cycling switch circuit and ground. If continuity is indicated, go to step 51 . If continuity is not indicated, go to step 54 .
  28. If A/C fuse (10 amp) is blown, go to step 52 . If A/C fuse is okay, go to next step.
  29. Remove A/C clutch relay from underhood electrical center. Using test light connected to battery voltage, probe A/C clutch relay ignition supply circuit on fuse side. If test light come on, go to step 52 . If test light does not come on, go to next step.
  30. Disconnect A/C compressor clutch connector. Using test light connected to battery voltage, probe A/C compressor clutch supply circuit terminal (Dark Green wire). If test light comes on, go to step 53 . If test light does not come on, replace A/C compressor clutch.
  31. Turn ignition switch to OFF position. Disconnect PCM connector C2. Using DVOM, check continuity of A/C relay control circuit between PCM and underhood electrical center (Dark Green/White wire). If continuity is indicated, go to step 54 . If continuity is not indicated, go to step 56 .
  32. Repair open in circuit that did not turn test light on. Recheck system operation.
  33. Repair open in A/C clutch circuit between relay and clutch. Recheck system operation.
  34. Replace A/C clutch relay. Recheck system operation.
  35. Check for proper terminal contact at A/C compressor clutch. If poor connection is found, repair as necessary and recheck system operation. If connections are okay, replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING.
  36. Repair open in A/C clutch ground circuit (Black wire). Recheck system operation.
  37. Repair short to voltage in A/C request circuit (Dark Green/White wire) between A/C high pressure cut-out switch and PCM. Recheck system operation.
  38. Repair short to voltage in circuit that had continuity. Recheck system operation.
  39. Repair short to voltage in Dark Green wire between A/C clutch relay and A/C compressor clutch. Recheck system operation.
  40. Replace A/C clutch relay. Recheck system operation.
  41. Repair short to ground in Dark Green/White wire between A/C clutch relay and PCM. Recheck system operation.
  42. Repair short to ground in circuit that had continuity. Recheck system operation.
  43. Check for proper terminal contact at A/C high pressure cut-out switch. Repair as necessary and recheck system operation. If connections are okay, go to next step.
  44. Replace A/C high pressure cut-out switch. Recheck system operation.
  45. Repair open in Dark Green/White wire between A/C high pressure cut-out switch and PCM. Recheck system operation.
  46. Repair short to ground in Dark Green/White wire between A/C high pressure cut-out switch and PCM. Recheck system operation.
  47. Check for proper terminal contact at A/C compressor cycling switch. Repair as necessary and recheck system operation. If connections are okay, go to next step.
  48. Replace A/C compressor cycling switch. Recheck system operation.
  49. Repair open in A/C compressor cycling switch ground circuit (Black wire). Recheck system operation.
  50. Repair open in A/C compressor cycling switch signal circuit (Dark Green wire). Recheck system operation.
  51. Repair short to ground in A/C compressor cycling switch signal circuit (Dark Green wire). Recheck system operation.
  52. Replace underhood electrical center. Recheck system operation.
  53. Check for, and repair, short to ground in Dark Green wire. If wire is okay, replace shorted A/C compressor clutch diode. Recheck system operation.
  54. Check for proper terminal contact at PCM. Repair as necessary and recheck system operation. If connections are okay, go to next step.
  55. Replace PCM and program. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. Recheck system operation.
  56. Repair open in A/C clutch relay control circuit (Dark Green/White wire) between underhood fuse block and PCM. Recheck system operation.

Intermittent conditions can be caused by poor connections, rubbed wire through insulation or a broken wire within the insulation. Check circuits thoroughly. For additional information, see appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.

  1. Before using this table confirm A/C system has an adequate state of charge. If A/C system has an adequate state of charge, go to next step. If A/C system does not have an adequate state of charge, see CHARGING A/C SYSTEM in GENERAL SERVICING PROCEDURES article.
  2. Start engine. Idle engine until normal operating temperature is reached. Leave engine at normal idle. Turn A/C on. If A/C clutch engages within 60 seconds, see «DIAGNOSTIC AIDS»(ref-96385-S24538278842001050300000) . If A/C clutch does not engage within 60 seconds, go to next step.
  3. Turn ignition switch to OFF position. Install scan tool. Start engine. Turn A/C on. Monitor A/C REQUEST in scan tool data list. If A/C REQUEST is YES, go to next step. If A/C REQUEST is not YES, go to step 14 .
  4. Using scan tool, monitor A/C EVAPORATOR SWITCH. If scan tool indicates switch is CLOSED, go to step 8 . If scan tool does not indicate switch is CLOSED, go to next step.
  5. Turn ignition switch to OFF position. Disconnect A/C cycling switch connector. Turn ignition switch to ON position, with engine off. Connect fused jumper between Dark Green wire at A/C cycling switch connector and ground. If scan tool indicates switch is CLOSED, go to next step. If scan tool does not indicate switch is CLOSED, go to step 27 .
  6. Using test light connected to battery voltage, probe Black/White wire of A/C cycling switch connector. If test light is on, go to next step. If test light is off, go to step 30 .
  7. Replace A/C cycling switch. After repairs, go to step 32 .
  8. Turn ignition switch to OFF position. Disconnect A/C compressor clutch connector. Start engine. Turn A/C on. Using test light connected to ground, probe A/C clutch voltage supply circuit (Dark Green wire) at A/C compressor clutch connector. If test light is on, go to next step. If test light is off, go to step 16 .
  9. Using test light connected to battery voltage, probe A/C clutch ground circuit (Black wire) at A/C clutch connector. If test light is on, go to step 11 . If test light is off, go to next step.
  10. Repair A/C clutch ground circuit (Black wire). After repairs, go to step 32 .
  11. Check A/C compressor clutch connector for poor connections. If problem was found, go to next step. If problem was not found, go to step 13 .
  12. Repair A/C compressor clutch connector. After repairs, go to step 32 .
  13. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 32 .
  14. Turn ignition switch to OFF position. Disconnect VCM connector C3. Turn ignition switch to ON position, with engine off. Turn A/C on. Using test light connected to ground, probe VCM connector C3 terminal No. 25 (Dark Green/White wire). If test light is on, go to step 29 . If test light is off, go to next step.
  15. Check A/C request signal circuit (Dark Green/White wire and Light Green wire) for open between HVAC control module and VCM. If problem was found, go to step 30 . If problem was not found, go to step 28 .
  16. Reconnect A/C clutch connector. Install scan tool. Turn ignition switch to ON position, with engine off. Using scan tool, command A/C relay on. If A/C relay clicks, go to step 22 . If A/C relay does not click, go to next step.
  17. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe ignition voltage circuit (Pink wire) at A/C relay connector. If test light is on, go to step 19 . If test light is off, go to next step.
  18. Repair open in A/C relay ignition voltage circuit (Pink wire). If fuse is blown, repair short to ground in Pink wire. After repairs, go to step 32 .
  19. Using test light connected to battery voltage, probe A/C relay control circuit (Dark Green/White wire) at A/C compressor clutch relay connector. Using scan tool, command A/C compressor clutch relay on. If test light is on, go to step 25 . If test light is off, go to next step.
  20. Check for open or short to voltage in Dark Green/White wire between underhood fuse block and VCM connector C3. If problem was found, go to next step. If problem was not found, go to step 29 .
  21. Repair Dark Green/White wire between underhood fuse block and VCM connector C3. After repairs, go to step 32 .
  22. Remove A/C compressor clutch relay. Using test light connected to ground, probe battery feed circuit (Orange wire) at A/C compressor clutch relay connector. If test light is on, go to step 24 . If test light is off, go to next step.
  23. Repair open in A/C compressor clutch relay battery feed circuit. If fuse is blown, repair short to ground in Orange wire. After repairs, go to step 32 .
  24. Turn ignition switch to ON position, with engine off. Using fused jumper wire, connect battery feed circuit and A/C compressor clutch voltage supply circuit (Dark Green wire) at A/C compressor clutch relay connector. If A/C clutch engages, go to next step. If A/C clutch does not engage, go to step 26 .
  25. Replace A/C compressor clutch relay. After repairs, go to step 32 .
  26. Repair open or short to ground in A/C compressor clutch voltage supply circuit (Dark Green wire). After repairs, go to step 32 .
  27. Check for open in A/C cycling switch signal circuit (Dark Green wire). If problem was found, go to step 30 . If problem was not found, go to step 29 .
  28. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 32 .
  29. Check VCM connectors for poor connections. If problem was found, go to next step. If problem was not found, go to step 31 .
  30. Repair circuit as necessary. After repairs, go to step 32 .
  31. Replace VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  32. Start engine. Idle engine until normal operating temperature is reached. Leave engine at normal idle. Turn A/C on. A/C clutch should engage within 60 seconds. Using scan tool, check for DTCs. If DTCs are not present, system is okay.

Intermittent conditions can be caused by poor connections, rubbed wire through insulation or a broken wire within the insulation. Check circuits thoroughly. For additional information, see appropriate MANUAL A/C-HEATER SYSTEMS article.

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
  2. Turn ignition on, engine off. Try to establish scan tool communication with HVAC control module, Body Control Module (BCM) and Powertrain Control Module (PCM)/Vehicle Control Module (VCM). If communication with all modules is established, go to next step. If communication with all modules is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
  3. Select display DTC function for each module. Record all displayed DTCs, status of displayed DTCs and which module set DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S41745044392001050400000) or «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S07918964952001050400000) .
  4. If scan tool displays DTCs beginning with "B", see appropriate SELF-DIAGNOSTICS article in BODY CONTROL MODULES. If scan tool displays DTCs beginning with "P", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.

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