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 applies and monitors 5 volts 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 pulled low through sensor ground circuit No. 736. This monitored voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).

Code B112 will set if: ignition is on, Outside Air Temperature (OAT) sensor has not failed, OAT reads greater than 32°F (0°C) and signal voltage indicates less than -29°F (-34°C), which is open circuit voltage, or greater than 209°F (85°C), which is shorted circuit voltage. During the time failure is present, a substitute temperature reading (same value as outside air temperature) will be used to allow continued operation of climate control system, and compressor clutch will be disabled. The actual A/C low side temperature sensor reading is indicated by BCM data display BD28.

1. Checks to see if open circuit reading is due to circuit or sensor. If open circuit reading changes to a shorted circuit reading after jumping sensor terminals, BCM and wiring are okay.
2. By applying a ground to various points in circuits, an open can be isolated by observing whether parameter display can be changed from open reading to shorted reading.
3. Checks to see if shorted circuit reading is due to circuit or sensor. If reading changes from shorted circuit to open circuit after disconnecting sensor, BCM and wiring are okay.