Part 1 of 2

Code B445 - A/C Compressor Engage Circuit (Part 1 of 2):

Wiring Diagram for Code B445 - A/C Compressor Engage Circuit:

CODE B445 - A/C COMPRESSOR ENGAGE CIRCUIT

Circuit Description:

If, by the sensors and HVAC mode selection, the BCM determines the A/C compressor should be on, it sends a signal to the ECM over the serial data line (CKT 800). If the ECM then determines that there is no reason to hold the compressor off, such as heavy engine loads, it will signal the A/C power module to turn the compressor on (CKT 762). The ECM will signal the BCM, over the data line, if it turned the compressor on and if the power steering switch is open which would hold the compressor off. Since the BCM receives a signal from the A/C low side temperature sensor, it can determine if the compressor really did come on as the low side temperature should drop when the compressor starts operating.

Code B445 will set if the engine is running and the ECM signaled the BCM that it turned the compressor on but the BCM did not see a change in the A/C low side temperature. During the time the failure is present the BCM will disable the A/C clutch for the entire ignition cycle. This is to protect the compressor from damage or belt breakage.


Test Description:

1. Checks to see if the fault is due to a circuit problem or a mechanical/refrigerant problem. If the clutch can be cycled by output function E008, the circuits controlling the clutch are OK.

2. Checks to see if the fault is due to a problem in the winding side and circuitry of the relay or the contact side and circuitry of the relay. If a testlight is put in place of the windings of the relay and the testlight lights, the winding side of the relay and its circuitry are OK.

3. Checks to see if the fault is due to the loss of feed voltage to the relay contacts or the relay circuits to the clutch including the relay.

4. Checks to see if the fault is due to the relay or the circuits to the clutch.

5. Checks to see if the fault is due to the clutch or the power and ground circuits to it.

6. Checks to see if the fault is due to an intermittent circuit problem or a mechanical/refrigerant problem.


Note on Intermittents:

If an intermittent Code B445 is being set, manipulate the related wiring in output function and watch for clutch to cycle.