The rear compartment occupant sensor is connected to battery voltage and ground at all times. When a combination of a difference in temperature compared to ambient and movement is detected by the sensor and the ignition is off, the BCM will command the horn to chirp and command the trunk to release within 3 minutes of a detect signal from the sensor. If the ignition is in the on position when the BCM receives the detect signal, the disable switch on the rear compartment occupant sensor will flash.

The rear compartment occupant sensor can be disabled by pressing the disable switch on the sensor and holding for 2 seconds. The BCM will command the trunk ajar telltale on for 1 minute with each ignition on signal while the sensor is disabled. Once the trunk is opened the sensor will reset to on and resume normal operation. The sensor can also be enabled inside of the trunk with the ignition on or off by pressing the disable switch. The trunk ajar switch signal circuit is used for rear compartment occupant sensor class 2 data.

The body control module (BCM) receives an invalid status from the rear compartment occupant sensor.

The service engine soon telltale is illuminated on the instrument cluster when the ignition is in the RUN position.

Diagnostic trouble code B3904 will be stored.

If the DTC is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.