P0645

DTC P0645

Circuit Description

Ignition voltage is supplied directly to the A/C compressor clutch relay. The powertrain control module (PCM) controls the relay by grounding the control circuit through 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 PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0645 Air Conditioning Clutch Relay Control Circuit

Conditions for Running the DTC

* The ignition voltage is between 9-18 volts.
* The PCM driver is activated for at least 0.5 second.

Conditions for Setting the DTC

The PCM detects an improper voltage level on the output circuit that controls the A/C relay.

Action Taken When the DTC Sets

* The PCM will not illuminate the malfunction indicator lamp (MIL).
* The PCM stores the failure records.
* The A/C compressor clutch is disabled.

Conditions for Clearing the DTC

* The DTC will become history if the PCM no longer detects a failure.
* The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
* The DTC can be cleared with a scan tool.

Test Description

Step 1 - Step 13:

Step 14:

The numbers below refer to the step numbers on the diagnostic table.
3. Listen for an audible click when the A/C compressor clutch relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.
4. This step tests for voltage at the coil side of the A/C compressor clutch relay. The 10-amp fuse supplies power to the coil side of the A/C compressor clutch relay.
5. This step verifies that the PCM is providing ground to the A/C compressor clutch relay.
6. This step tests if ground is constantly being applied to the A/C compressor clutch relay.
7. This step tests for a short to voltage or an open.
13. Perform the programming procedure for the PCM.