1987 Cadillac SevilleFACTORY OEM SERVICE PROCEDURE

Code B113 - In-Car 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 in-car air temperature sensor uses a thermistor to control signal voltage to BCM. The BCM applies 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 (0) volts (shorted circuit).

Code "B113" will set if signal voltage indicates less than -144°F/-96°C (open circuit) or over 189°F/87°C (shorted circuit). These conditions can be observed in BCM data display (parameter "BD25") as an "IN-CAR TEMP" reading outside the range of -144 to 189°F (-34 to 96°C).

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. If shorted circuit reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are okay.
  2. If open circuit reading changes to shorted circuit reading after jumpering 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 sensor, BCM and wiring are okay.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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