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Air Conditioning Compressor Malfunction




Air Conditioning Compressor Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

Ignition voltage is supplied directly to the A/C compressor clutch relay. The engine control module (ECM) controls the relay by grounding the A/C CMPRSR CLTCH relay control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. The driver has a fault line which is monitored by the ECM. When the ECM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this DTC will set.

The ECM will monitor the control circuit for the following:

* A short to ground
* A short to voltage
* An open circuit
* An open relay coil
* An internally shorted or excessively low resistance relay coil

When the ECM detects any of the above malfunctions, the A/C compressor clutch is disabled.

Diagnostic Aids

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

* Battery voltage is between 9-18 volts.
* Engine coolant temperature (ECT) is less than 123°C (253°F).
* Engine speed is less than 4760 RPM.
* Engine speed is more than 600 RPM.
* A/C high side pressure is between 2929-269 kPa (425-39 psi).
* Throttle position is less than 100 percent.
* Evaporator temperature is greater than 0°C (32°F).
* ECM does not detect excessive torque load.
* ECM does not detect insufficient idle quality.

Reference Information
Schematic Reference

HVAC Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

* Air Delivery Description and Operation (Air Delivery Description and Operation)
* Air Temperature Description and Operation (Air Temperature Description and Operation)

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Verification

1. Ignition ON, observe the scan tool A/C High Side Pressure Sensor parameter, the reading should be between 2929-269 kPa (425-39 psi).

• If the reading is not within the specified range, refer to A/C Refrigerant Pressure Sensor Malfunction.

2. Observe the function of the HVAC compressor while commanding the A/C relay ON and OFF with a scan tool, the A/C compressor clutch should engage and disengage when changing between the commanded states.

• If the A/C compressor does not engage or does not disengage, refer to A/C Compressor Malfunction.

Circuit/System Testing

A/C Refrigerant Pressure Sensor Malfunction
1. Ignition OFF, disconnect the harness connector at the A/C refrigerant pressure sensor.
2. Ignition OFF, test for less than 1.0 ohm between the low reference circuit terminal A and ground.

• If greater than the specified range, test the low reference circuit terminal A for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal B and ground.

• If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
• If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Verify the scan tool A/C High Side Pressure Sensor parameter is less than 0.2 volts (9 psi).

• If greater than 0.2 volts (9 psi), test the signal circuit terminal C for a short to voltage. If the circuit tests normal, replace the ECM.

5. Install a 3-amp fused jumper wire between the signal circuit terminal C and the 5-volt reference circuit terminal B. Verify the scan tool A/C High Side Pressure Sensor parameter is greater than 4.90 volts (453 psi).

• If less than 4.90 volts (453 psi), test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

6. If all circuits test normal, replace the A/C refrigerant pressure sensor

A/C Compressor Malfunction
1. Ignition OFF, disconnect the A/C CMPRSR CLTCH relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal and ground.

• If the test lamp illuminates, test the control circuit for a short to voltage.

3. Verify that a test lamp illuminates between the ignition circuit terminal and ground.

• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test or replace the A/C CMPRSR CLTCH relay.

4. Verify that a test lamp illuminates between the B+ circuit terminal and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+, ignition circuit fuse is open, test the control circuit terminal for a short to ground.

5. Disconnect the harness connector at the A/C compressor clutch.
6. Test for less than 1.0 ohm between the A/C compressor clutch ground circuit terminal 2 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the A/C compressor clutch.
8. Connect a 10A fused jumper wire between the B+ circuit terminal and the control circuit terminal. Verify the A/C compressor clutch is activated.

• If the A/C compressor clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the A/C compressor.

9. Connect a test lamp between the ignition circuit terminal and the control circuit terminal.
10. Command the A/C relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

11. If all circuits test normal, test or replace the A/C CMPRSR CLTCH relay.

Component Testing

Relay Test
1. Ignition OFF, disconnect the A/C CMPRSR CLTCH relay.
2. Test for 60-180 ohms of resistance between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay

3. Test for infinite resistance between the following terminals:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87

• If not the specified value, replace the relay.

4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

• If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Compressor Clutch Assembly Replacement (Service and Repair)
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement (LNJ) (Service and Repair)Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement (LY7) (Service and Repair)
* Control Module References (Programming and Relearning)for ECM replacement, setup and programming

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