DTC Description
This diagnostic procedure covers DTC P0645, A/C Relay Circuit Malfunction.
Circuit Description
The engine control relay applies battery voltage to the coil circuit of the air conditioning (A/C) clutch relay through the ignition circuit. Using a device called a Driver, the engine control module (ECM) grounds control circuit for the A/C clutch relay to activate the A/C clutch and operate the A/C compressor. Refer to General Air Conditioning (A/C) System Description and Operation for details for the A/C compressor operation.
The Driver has a feedback circuit that is pulled up to a voltage. The ECM monitors the Driver feedback circuit to determine if the control circuit is open, shorted to ground, or shorted to a positive voltage.
An A/C clutch relay control circuit DTC sets if the ECM detects a fault condition in the A/C clutch relay control circuit.
Conditions for Running the DTC
| • | The ignition is ON and the A/C is switched ON. |
| • | Information not available at time of publication. |
Conditions for Setting the DTC
The PCM detects that the commanded state of the driver and the actual state of the circuit do not match.
Conditions for Clearing the DTC
The Vehicle Speed Output Circuit DTC is a Type C DTC. Refer to Engine Controls System Component Description for action taken when a Type C DTC sets and Conditions for Clearing a Type C DTC.
Additional Information
| • | Refer to Automatic HVAC System Description for details of the A/C system operation. |
| • | For diagnosis on any further concerns with the A/C system, refer to General Air Conditioning (A/C) System Description and Operation. |
| • | For an intermittent fault condition, refer to Testing for Intermittent Conditions and Poor Connections. |
| • | Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic procedure for shorted terminals or poor wiring connection before replacing any component. Refer to Testing for Intermittent Conditions and Poor Connections for information on electrical fault diagnosis. |
| • | Refer to HVAC Schematics and HVAC Connector End Views to aid in the diagnosis procedures. |
Step | Action | Yes | No |
|---|---|---|---|
1 | Was the Main Diagnostic Table performed? | Go to Step 2 | Refer to Diagnostic System Check - HVAC Systems - Automatic |
2 |
Does DTC P0645 fail this ignition cycle? | Go to Step 3 | Refer to Diagnostic Aids for the A/C Clutch Relay Control Circuit DTC |
3 |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 5 |
4 |
Does the test lamp turn ON and OFF when the A/C clutch relay is commanded ON and OFF? | Go to Step 7 | Go to Step 6 |
5 | Repair the high resistance or open circuit fault condition in the ignition voltage circuit of the A/C clutch relay. Refer to Wiring Repairs for information on electrical wiring repair procedures. Was the repair completed? | Go to Step 9 | -- |
6 | Test the control circuit of the A/C clutch relay for a high resistance, open circuit, short to ground or short to voltage fault condition. Refer to Testing for Intermittent Conditions and Poor Connections for information on electrical fault diagnosis. Was any fault found and rectified? | Go to Step 9 | Go to Step 8 |
7 | Replace the A/C clutch relay. Refer to Electrical Center Identification Views. Was the repair completed? | Go to Step 9 | -- |
8 | Replace the PCM. Refer to Powertrain Control Module Replacement. Was the repair completed? | Go to Step 9 | -- |
9 |
Do any of the A/C clutch relay control circuit DTCs fail this ignition cycle? | Go to Step 2 | Go to Step 10 |
10 | Using Tech 2, select the DTC display function. Are there any DTCs displayed? | Go to the appropriate DTC Table | System OK |
When all diagnosis and repairs are completed, check the powertrain management system for correct operation. | |||
