Code B111 - A/C High Side Temperature Sensor Circuit: Notes

The A/C high side temperature sensor is a thermistor that controls signal voltage to BCM. The BCM supplies voltage on circuit No. 732 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 B111 will set if ignition is on, outside air temperature sensor is functioning properly and reading above 0°C, and signal voltage indicates less than -34°C (open circuit) or more than 209°C (shorted circuit). During a failure, a substitute temperature reading is used to allow continued operation of A/C-heater system and A/C high side temperature reading BD27 will display actual sensor reading.

1. BCM data code BD27 displays A/C high side temperature. Normal range is from -34°C to 209°C.
2. Checks to see if open circuit reading is due to circuit or sensor. If open circuit reading changes to shorted circuit reading after jumping sensor terminals, BCM and wiring are okay.
3. By applying 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.
4. Checks if shorted circuit reading is caused by circuit or sensor. If shorted circuit reading changes to an open circuit reading after disconnecting the sensor, BCM and wiring are okay.