Code B112 - A/C Low Side Temperature Sensor Circuit: Notes

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

Code B112 will set if signal voltage indicates less than -34°C (open circuit) or more than 87°C (shorted circuit). During a failure, a substitute temperature reading (ambient temperature reading) is used to allow continued operation of climate control system. The A/C compressor clutch will also be disabled and A/C low side temperature reading BD28 will display actual sensor reading.

1. BCM data code BD28 displays A/C low side temperature. Normal range is from -34°C to 87°C.
2. Checks if open circuit reading is caused by circuit or sensor. If open circuit reading changes to shorted circuit reading after disconnecting sensor, BCM and wiring are okay.
3. By applying ground to various points in circuits, an open can be isolated by seeing if parameter display can be changed from open reading to shorted reading.
4. Checks to see if shorted circuit reading is caused by circuit or sensor. If shorted circuit reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are okay.