GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Impala 🢒 DTC 🢒 DTC B3898

Circuit Description

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.

Conditions for Setting the DTC

The body control module (BCM) does not receive a motion status after a set number of trunk openings.

Action Taken When the DTC Sets

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

Diagnostic trouble code B3898 will be stored.

Conditions for Clearing the DTC
    • Motion is detected by the sensor.
    • A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • A scan tool may be used to clear the DTC.

Diagnostic Aids

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

Step

Action

Yes

No

1

Did you perform the Body Rear End Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Body Rear End

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the rear compartment occupant sensor lighted disable switch.
  4. Inspect for obstructions around the sensor.
  5. Wave your hand under the sensor.

Does the lighted disable switch illuminate?

Go to Diagnostic Aids

Go to Step 3

3

Replace the rear compartment occupant sensor.

Did you complete the replacement?

Go to Step 4

--

4
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

System OK

Go to Step 2