P0645

DTC P0645

Circuit Description

The air conditioning (A/C) compressor clutch relay is controlled by the engine control module (ECM). Ignition 1 voltage is supplied directly to the A/C compressor clutch relay. The ECM controls the relay by grounding the 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. Each 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 volt. 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 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0645 Air Conditioning (A/C) Clutch Relay Control Circuit

Conditions for Running the DTC

* DTC P0606 is not set.

* The A/C is requested.

* The ignition 1 voltage is more than 11 volts.

* DTC P0645 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects an improper voltage level on the A/C clutch relay control circuit for 10 seconds.

Action Taken When the DTC Sets

* The control module stores the DTC information into memory when the diagnostic runs and fails.

* The malfunction indicator lamp (MIL) will not illuminate.

* The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

* The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

* A current DTC Last Test Failed clears when the diagnostic runs and passes.

* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

* Clear the DTC with a scan tool.

Diagnostic Aids

* For HVAC system concerns, refer to HVAC Preliminary Checks HVAC Preliminary Checks in Heating, Ventilation and Air Conditioning.

* If condition is intermittent, refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections in Wiring Systems.