BCM Code B113 - In-Car Temperature Sensor Circuit: Notes

The in-car air temperature sensor is a thermistor that controls signal voltage to BCM. The BCM supplies voltage on circuit No. 734 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 B113 will set if ignition is on, outside temperature sensor is working properly, ambient temperature is above -18°C and signal voltage indicates less than -34°C (open circuit) or more than 96°C (shorted circuit). During a failure, a substitute temperature reading is used to allow continued operation of A/C-heater system and in-car temperature reading BD25 will display actual sensor reading.

1. BCM data code BD25 displays in-car temperature. Normal range is -34°C to 96°C.
2. Checks if open circuit 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 observing whether 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 short circuit reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are okay.