BCM Code F11: A/C High Side Temp Sensor Circuit: Notes

WARNING: This page is about a different car, the 1990 Cadillac Fleetwood and 1990 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.

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. Refer to NOTE ON INTERMITTENTS at end of this text.

The A/C high side temperature sensor uses a thermistor to control signal voltage to BCM. The BCM applies and monitors 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 monitored signal voltage is pulled low through sensor ground, circuit No. 736. This signal voltage will vary between 5 volts (circuit open) and zero volts (circuit shorted).

Code F11 will set if signal voltage indicates an open circuit 16°F (-9°C), or a shorted circuit, 408°F (209°C). These conditions can be observed in BCM data display (parameter P.2.7) as a reading outside the range of 16°F to 408°F (-9°C to 209°C).

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) If temperature reading changes after disconnecting sensor, BCM and wiring are okay.

Test Number 2) If temperature reading changes after jumpering sensor terminals, BCM and wiring are okay.

Test Number 3) By applying ground to various points in circuits, an open can be isolated when temperature display changes from about 59°F to 392°F (-15°C to 200°C).