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Air Conditioning Compressor Malfunction

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

A/C Compressor Clutch Relay Coil Ignition

P0645, P0646

P0645, P0647

--

--

A/C Compressor Clutch Relay Switch B+

1

1

--

--

A/C Compressor Clutch Relay Coil Control

P0645, P0646

P0645, P0647

P0645, P0647

3

A/C Compressor Control

1

1

2

-

A/C Compressor Ground

1

1

--

--

1. A/C Compressor Inoperative

2. A/C Compressor Always ON

3. A/C Compressor Malfunction

Circuit/System Description

When the A/C switch is pressed, the HVAC control module sends an A/C request message to the engine control module (ECM) via CAN-Bus. Therefore the ECM grounds the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch. The A/C compressor clutch will be activated.

Diagnostic Aids

The following conditions must be met in order for the ECM to turn on the A/C compressor clutch:

    • Battery voltage is between 9-18 V.
    • Engine coolant temperature is less than 124°C (255°F).
    • Engine speed is greater than 600 RPM.
    • Engine speed is less than 5 500 RPM.
    • A/C high side pressure is between 269-2 929 kPa (39-425 PSI).
    • Throttle position is less than 100%.
    • Evaporator temperature is greater than 3°C (38°F).
    • ECM does not detect immoderate torque load.
    • ECM does not detect insufficient idle quality.
    • The ambient temperature is above 1°C (34°F).

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Manual HVAC Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

Note: Before executing Circuit/System Testing, all conditions shown in Diagnostic Aids must be met.

  1. Ignition ON, activate and deactivate the A/C switch. Verify the scan tool A/C Switch parameter changes between Active and Inactive.
    2. [ARW-LISTFAIL]

  2. If the parameter does not change

    Replace the A26 HVAC Controls.

    3. [/ARW-LISTFAIL][ARW-LISTPASS]

  3. If the parameter changes

    4. [/ARW-LISTPASS]
  4. Activate and deactivate the A/C switch. Verify the engine control module (ECM) scan tool A/C Request Signal parameter changes between Active and Inactive.
    5. [ARW-LISTFAIL]

  5. If the parameter does not change

    Replace the K33 HVAC Control Module.

    6. [/ARW-LISTFAIL][ARW-LISTPASS]

  6. If the parameter changes

    7. [/ARW-LISTPASS]
  7. Ignition OFF, remove the KR29 A/C Compressor Clutch Relay.
  8. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
    9. [ARW-LISTFAIL]

  9. If the test lamp does not illuminate and the circuit fuse is good

    10. [/ARW-LISTFAIL]
    4.1. Ignition OFF.
    4.2. Test for less than 2 Ω in the B+ circuit end to end.
    [ARW-LISTFAIL]

  10. If 2 Ω or greater, repair the open/high resistance in the circuit.

  11. If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.

    12. [/ARW-LISTFAIL] [ARW-LISTFAIL]

  12. If the test lamp does not illuminate and the circuit fuse is open

    13. [/ARW-LISTFAIL]
    4.1. Ignition OFF.
    4.2. Test for infinite resistance between the B+ circuit and ground.
    [ARW-LISTFAIL]

  13. If less than infinite resistance, repair the short to ground on the circuit.

    14. [/ARW-LISTFAIL][ARW-LISTPASS]

  14. If infinite resistance

    15. [/ARW-LISTPASS]
    4.3. Disconnect the harness connector at the Q2 A/C Compressor Clutch.
    4.4. Test for infinite resistance between the control circuit terminal 87 and ground.
    [ARW-LISTFAIL]

  15. If less than infinite resistance, repair the short to ground on the circuit.

    16. [/ARW-LISTFAIL][ARW-LISTPASS]

  16. If infinite resistance

    17. [/ARW-LISTPASS]
    4.5. Connect the harness connector at the Q2 A/C Compressor Clutch.
    4.6. Install a 10 A fused jumper wire between B+ and the control circuit terminal 87 and verify the fuse is good.
    [ARW-LISTFAIL]

  17. If the fuse is open, replace the Q2 A/C Compressor Clutch.

  18. If the fuse is good, replace the KR29 A/C Compressor Clutch Relay.

    19. [/ARW-LISTFAIL] [ARW-LISTPASS]

  19. If the test lamp illuminates

    20. [/ARW-LISTPASS]
  20. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    21. [ARW-LISTFAIL]

  21. If the test lamp illuminates

    Repair the short to voltage on the circuit.

    22. [/ARW-LISTFAIL][ARW-LISTPASS]

  22. If the test lamp does not illuminate

    23. [/ARW-LISTPASS]
  23. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the Q2 A/C Compressor Clutch is activated.
    24. [ARW-LISTFAIL]

  24. If the Q2 A/C Compressor Clutch is not activated

    25. [/ARW-LISTFAIL]
    6.1. Ignition OFF, disconnect the harness connector at the Q2 A/C Compressor Clutch.
    6.2. Test for less than 5 Ω between the ground circuit terminal A and ground.
    [ARW-LISTFAIL]

  25. If greater than 5 Ω, repair the open/high resistance in the circuit.

    26. [/ARW-LISTFAIL][ARW-LISTPASS]

  26. If less than 5 Ω

    27. [/ARW-LISTPASS]
    6.3. Test for less than 2 Ω in the control circuit end to end.
    [ARW-LISTFAIL]

  27. If 2 Ω or greater, repair the open/high resistance in the circuit.

  28. If less than 2 Ω, replace the Q2 A/C Compressor Clutch.

    29. [/ARW-LISTFAIL] [ARW-LISTPASS]

  29. If the Q2 A/C Compressor Clutch is activated

    30. [/ARW-LISTPASS]
  30. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
  31. Command the engine control module (ECM) A/C Relay output function ON and OFF with the scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    32. [ARW-LISTFAIL]

  32. If the test lamp always illuminates or does not illuminate

    Replace the K20 Engine Control Module.

    33. [/ARW-LISTFAIL][ARW-LISTPASS]

  33. If the test lamp illuminates as commanded

    34. [/ARW-LISTPASS]
  34. Replace the KR29 A/C Compressor Clutch Relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Air Conditioning Compressor Replacement
    •  Heater and Air Conditioning Control Replacement
    • Control Module References for HVAC control module or engine control module replacement, setup, and programming
   


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