B112

Chart:

Schematic:

DESCRIPTION
The A/C low side temperature sensor is a thermistor that controls the signal voltage to the Body Control Module (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 Volts (open CKT) and 0 Volts (shorted CKT).


Code B112 will set if the ignition is on, the outside temperature sensor has not failed and reads above 0°C (32°F) and the signal voltage indicates less than -34°C (-29°F) (open CKT) or over 87°C (189°F)(shorted CKT). During the time the failure is present a substitute temperature reading (the same value as outside air temperature) 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
The numbers below refer to circled numbers on the diagnostic chart:
1. BCM data value BD28 displays A/C lowside temperature. The normal range is from 34°C (93°F) to 87°C (189°F).
2. Check 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.
3. 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.
4. Check 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, 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 (129°F) to 87°C (189°F).


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