B112

Code B112:

Outside Temp Sensor Circuit:

CIRCUIT DESCRIPTION:

The A/C low side temperature sensor is a thermistor that senses refrigerant system low side (evaporator inlet) temperature for the BCM. The BCM applies a voltage on CKT 731 to the sensor. When the sensor is cold, its resistance is high, therefore the BCM will see a high signal voltage. As the sensor warms, its resistance becomes less and the signal voltage is pulled low through the sensor ground, CKT 736. This signal voltage will vary between 5.0 volts (open circuit) and 0 volts (shorted circuit).

Code B112 will set if the ignition is "ON," the outside temperature sensor has not failed and reads above 0°C and the signal voltage indicates less than -34°C (open circuit) or over 85°C (shorted to ground circuit). During the time the failure is present a substitute temperature reading will be implemented to allow continued operation of the climate control system, also the compressor clutch will be disabled. The A/C low side temperature reading BD28 will however, display the actual sensor reading.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if the open circuit reading is due to the circuit or the sensor. If the open circuit reading changes to a shorted circuit reading after jumping the sensor terminals, the BCM and wiring are OK.

2. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.

3. Checks to see if the shorted circuit reading is due to the circuit or the sensor. If the shorted circuit reading changes to an open circuit reading after disconnecting the sensor, the BCM and wiring are OK.

NOTE ON INTERMITTENTS:

If an intermittent code B112 is being set, check the B112 snap data value for low disde temperature, BD28. If the BD28 value is under -34°C, the code was caused by an open in circuit 731, circuit 736, or the low side temp sensor. If the BD28 value is over 85°C, the code was caused by a short to ground on circuit 731 or a shorted low side temp sensor. Manipulate the related wiring while observing BCM data BD28. If the failure is induced, the reading will jump from its normal value to a reading outside the range of -34°C to 85°C.

If the value of the sensor displayed by BD28 is not reasonably close to the corresponding gauge pressure reading, check for poor terminal contact or replace sensor.