1987 Cadillac SevilleFACTORY OEM SERVICE PROCEDURE

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

NOTE: If this code is not displayed during second pass of diagnostic codes, it is an intermittent failure and cannot be diagnosed using this procedure.

The A/C high side temperature sensor uses a thermistor to control signal voltage to BCM. The BCM applies 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 (0) volts (shorted circuit).

Code "B111" will set if signal voltage indicates less than 16°F/-9°C (open circuit) or over 408°F/209°C (shorted circuit). These conditions can be observed in BCM data display (parameter "BD27") as a reading outside the range of 16-408°F (-9°C to 209°C).

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. BCM data value "BD27" displays "AC High Side Temperature". The normal range is from -29°F to 408°F (-34°C to 209°C).
  2. Check 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. Check to see if shorted circuit reading is due to circuit or sensor. If shorted circuit reading changes to an open circuit reading after disconnecting the sensor, BCM and wiring are okay.
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