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:

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

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

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

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.

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.

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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.