P0645

CIRCUIT DESCRIPTION
Ignition 1 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. If the fault detection circuit senses a voltage other than what is expected, this DTC will set.

CONDITIONS FOR RUNNING THE DTC
^ The ignition voltage is between 6.0-18.0 volts.
^ The engine speed is greater than 400 RPM.

CONDITIONS FOR SETTING THE DTC
^ Commanded state does not equal actual state of the control circuit.
^ The condition is present for at least 5 seconds.

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

Steps 1-3:

Steps 4-13:

The numbers below refer to the step numbers on the diagnostic table.
2. 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.
3. Tests for ignition 1 voltage at the coil side of the A/C compressor clutch relay. The 15 Amp fuse supplies ignition 1 voltage to the coil side of the A/C compressor clutch relay.
4. Verifies that the powertrain control module is providing ground to the A/C compressor clutch relay.
5. Tests if ground is constantly being applied to the A/C compressor clutch relay.
6. Tests for a short to voltage or an open.
12. Perform the recalibration procedure for the powertrain control module.