BCM Code F12, A/C Low Side Temperature Sensor Circuit: Description

NOTE: If this code is not displayed during second pass of diagnostic codes, it is an intermittent failure and cannot be diagnosed using this procedure. Refer to NOTE ON INTERMITTENTS at end of this text.

The A/C low side temperature sensor uses a thermistor to control signal voltage to BCM. The BCM applies and monitors voltage on circuit No. 731 to sensor. When sensor is cold, its resistance is high; therefore, BCM will see a high monitored voltage. As sensor warms, its resistance becomes less and signal voltage is lowered through sensor ground circuit No. 736. This signal voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).

BCM Code F12 will set if signal voltage indicates an open circuit, temperature less than -29°F (-34°C); or shorted circuit, temperature greater than 189°F (87°C). These conditions can be observed in BCM data display (parameter P.2.8) as a reading outside the range of -29°F to 189°F (-34°C to 87°C).