P0645
DTC P0645CIRCUIT 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 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 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 11.0 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 in Heating, Ventilation, and Air Conditioning. - Preliminary Checks
- If condition is intermittent refer to Diagnostic Aids for Circuit Testing and Wiring Repair Procedures.
TEST
Steps 1-3:
Steps 4-8:
Steps 9-12:
