Code B445, A/C Compressor Engage Circuit: Notes
By the sensors and mode selection, the BCM will determine if the A/C compressor should be on. It will send a signal to the ECM over the serial data line (circuit 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 (circuit 762). The ECM will signal the BCM, over the serial data line, if it turned the compressor on or if the power steering cut-out switch is open (that could 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 to turn 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.
- 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 EO08, the circuits controlling the clutch are okay.
- 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 test light is put in place of the windings of the relay and the test light glows, the winding side of the relay and its circuitry are okay.
- 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.
- Checks to see if the fault is due to the relay or the circuits to the clutch.
- Checks to see if the fault is due to the clutch or the power and ground circuits to it.
- Checks to see if the fault is due to an intermittent circuit problem or a mechanical/refrigerant problem.