P0645

DTC P0645

CIRCUIT DESCRIPTION
Ignition voltage is supplied directly to the A/C compressor clutch relay. The engine control module (ECM) 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 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.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0645 Air Conditioning (A/C) Clutch Relay Control Circuit

CONDITIONS FOR RUNNING THE DTC
- The ignition voltage is between 9-18 volts.
- The ECM driver is activated for at least 0.5 second.

CONDITIONS FOR SETTING THE DTC
The ECM detects an improper voltage level on the output circuit that controls the A/C relay.

ACTION TAKEN WHEN THE DTC SETS
- The ECM will not illuminate the malfunction indicator lamp (MIL).
- The ECM stores the failure records.
- The A/C compressor clutch is disabled.

CONDITIONS FOR CLEARING THE DTC
- The diagnostic trouble code (DTC) will become history if the ECM 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. A 15-amp fuse supplies power to the coil side of the A/C compressor clutch relay.
5. This step verifies that the ECM 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.
13. Perform the programming procedure for the ECM.