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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

Automatic 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]
  3. If the parameter does not change

    Replace the A26 HVAC Controls.

  4. [/ARW-LISTFAIL][ARW-LISTPASS]
  5. If the parameter changes

  6. [/ARW-LISTPASS]
  7. 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.
  8. [ARW-LISTFAIL]
  9. If the parameter does not change

    Replace the K33 HVAC Control Module.

  10. [/ARW-LISTFAIL][ARW-LISTPASS]
  11. If the parameter changes

  12. [/ARW-LISTPASS]
  13. Ignition OFF, remove the KR29 A/C Compressor Clutch Relay.
  14. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
  15. [ARW-LISTFAIL]
  16. If the test lamp does not illuminate and the circuit fuse is good

  17. [/ARW-LISTFAIL]
    4.1. Ignition OFF.
    4.2. Test for less than 2 Ω in the B+ circuit end to end.
    [ARW-LISTFAIL]
  18. If 2 Ω or greater, repair the open/high resistance in the circuit.

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

  20. [/ARW-LISTFAIL] [ARW-LISTFAIL]
  21. If the test lamp does not illuminate and the circuit fuse is open

  22. [/ARW-LISTFAIL]
    4.1. Ignition OFF.
    4.2. Test for infinite resistance between the B+ circuit and ground.
    [ARW-LISTFAIL]
  23. If less than infinite resistance, repair the short to ground on the circuit.

  24. [/ARW-LISTFAIL][ARW-LISTPASS]
  25. If infinite resistance

  26. [/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]
  27. If less than infinite resistance, repair the short to ground on the circuit.

  28. [/ARW-LISTFAIL][ARW-LISTPASS]
  29. If infinite resistance

  30. [/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]
  31. If the fuse is open, replace the Q2 A/C Compressor Clutch.

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

  33. [/ARW-LISTFAIL] [ARW-LISTPASS]
  34. If the test lamp illuminates

  35. [/ARW-LISTPASS]
  36. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
  37. [ARW-LISTFAIL]
  38. If the test lamp illuminates

    Repair the short to voltage on the circuit.

  39. [/ARW-LISTFAIL][ARW-LISTPASS]
  40. If the test lamp does not illuminate

  41. [/ARW-LISTPASS]
  42. 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.
  43. [ARW-LISTFAIL]
  44. If the Q2 A/C Compressor Clutch is not activated

  45. [/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]
  46. If greater than 5 Ω, repair the open/high resistance in the circuit.

  47. [/ARW-LISTFAIL][ARW-LISTPASS]
  48. If less than 5 Ω

  49. [/ARW-LISTPASS]
    6.3. Test for less than 2 Ω in the control circuit end to end.
    [ARW-LISTFAIL]
  50. If 2 Ω or greater, repair the open/high resistance in the circuit.

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

  52. [/ARW-LISTFAIL] [ARW-LISTPASS]
  53. If the Q2 A/C Compressor Clutch is activated

  54. [/ARW-LISTPASS]
  55. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
  56. 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.
  57. [ARW-LISTFAIL]
  58. If the test lamp always illuminates or does not illuminate

    Replace the K20 Engine Control Module.

  59. [/ARW-LISTFAIL][ARW-LISTPASS]
  60. If the test lamp illuminates as commanded

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Air Conditioning Compressor Replacement : 2.4L LAF → LNP → 1.6L LDE and 1.8L 2H0
    •  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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