BCM Code F13, In-Vehicle Temperature Sensor: 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. Refer to NOTE ON INTERMITTENTS.

In-vehicle temperature sensor uses a thermistor to control signal voltage to BCM. BCM applies and monitors voltage on circuit No. 734 to sensor. When sensor is cold, its resistance is high (BCM will read a high monitored voltage). As sensor warms, its resistance decreases and signal voltage is pulled low through sensor ground circuit No. 736. This signal will vary between 5 volts (open circuit) and zero volts (shorted circuit). Code F13 will set if signal voltage indicates less than -29°F (-34°C) or greater than 205°F (96°C). These conditions can be observed in BCM data display as an in-vehicle temperature reading (parameter P.2.5) outside range.

NOTE: Test numbers refer to numbers on diagnostic chart.

If temperature reading changes after disconnecting sensor, BCM and wiring are okay.
If temperature reading changes after jumpering sensor terminals, BCM and wiring are okay.
By applying a ground to various points in circuit, an open can be isolated when display changes to outside range of -29°F to 194°F (-34°C to 90°C).