B111

BCM Code B111:

Twilight Photocell Circuit:

CIRCUIT DESCRIPTION:
The A/C high side temperature sensor is a thermistor that controls the signal voltage to the BCM. The BCM applies a voltage on CKT 732 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 5V (open circuit) and 0V (shorted circuit).

Code B111 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 -30°C (open circuit) or over 184°C (shorted circuit). During the time the failure is present, a substitute temperature reading of 56°F will be implemented to allow continued operation of the climate control system and the engine cooling fans will be forced to high speed if the A/C clutch is "ON." The A/C high side temperature reading BD27 will, however, display the actual sensor reading.

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

1. BCM data value BD27 displays A/C high side temperature. The normal range is from - 30°C to 184°C.
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.

NOTES ON INTERMITTENTS:
If Code B112 is also set, the most likely cause for these codes is an open in CKT 736 between splice S214 and BCM pin "2A1."

If an intermittent Code B111 is being set manipulate the related wiring while observing BCM data BD27. If the failure is induced, the reading will jump from its normal value to a reading outside the range of -30°C to 184°C.

If the value of the sensor, displayed by BD27, is not reasonably close to the corresponding gage pressure reading, check for poor terminal contact or replace sensor.