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Codes B446, B447, B448:

A/C Circuit:

CIRCUIT DESCRIPTION:

The BCM monitors certain system inputs for an indication of low refrigerant charge. If the system refrigerant state of charge should fall below approximately one third its capacity, the BCM is capable of detecting this condition and will display a driver warning message to warn the operator. The BCM determines the state of charge by its low side temperature sensor and the low refrigerant pressure switch. Since temperature and pressure are proportionally related in the A/C system, a low temperature is the same as low pressure. In addition to the message, the BCM will store in memory a diagnostic code B446, B447, or B448 to indicate that a low refrigerant condition was detected.

Code B446 will set if the low side temperature drops too quickly during compressor engagement. Code B447 will set if the low side temperature drops much too quickly during compressor engagement or the low refrigerant pressure switch opens during compressor engagement. Code B448 will set if the low refrigerant pressure switch remains open for more than 3.0 minutes.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. BCM input value BI08 displays the voltage state of the circuit at the BCM.

2. Checks to see if the open circuit reading is due to the circuit or the switch.

3. Checks to see if the fault is on the ignition side or the BCM side of the switch circuit.

4. This step checks to see if the fault is due to the pressure switch or a low refrigerant charge.