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) detects an open or short to battery positive in the Trunk Ajar Switch Signal circuit. |
| • | The body control module (BCM) detects a loss of Battery Positive Voltage, Ignition 0 Voltage, or Ground for the Rear Compartment Occupant Sensor. |
| • | The BCM detects the open or short for more than 2 seconds. |
Action Taken When the DTC Sets
The service engine soon telltale is illuminated on the instrument cluster.
Diagnostic trouble code B3896 will be stored.
Conditions for Clearing the DTC
| • | An open or short is no longer detected in either the trunk ajar switch signal, battery positive voltage, ignition 0 voltage, or ground circuits. |
| • | 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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step will ensure that the DTC is not a history code.
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Tests for the proper operation of the circuit in the high voltage range.
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Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper wire opens when you perform this test, the signal circuit is shorted to voltage.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Body Rear End Diagnostic System Check? | -- | Go to Step 2 | |
Is DTC B3896 current? | -- | Go to Step 3 | Go to Diagnostic Aids | |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 4 | |
Measure the voltage between the trunk ajar switch signal circuit and a good ground. Does the voltage measure near the specified voltage? | B+ | Go to Step 5 | Go to Step 10 | |
5 | Connect a test lamp between the rear compartment occupant sensor battery positive voltage circuit and a good ground. Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 11 |
6 | Connect a test lamp between the rear compartment occupant sensor battery positive voltage circuit and the rear compartment occupant sensor ground circuit. Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 12 |
7 | Connect a test lamp between the Ignition 0 Voltage circuit and a good ground. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 13 |
8 | Inspect for poor connections at the harness connector of the rear compartment occupant sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 |
9 | Test the trunk ajar switch signal circuit of the rear compartment occupant sensor for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 |
10 | Test the trunk ajar switch signal circuit of the rear compartment occupant sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 |
11 | Repair the open, high resistance, or short to ground in the battery positive voltage circuit of the rear compartment occupant sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | -- |
12 | Repair the open or high resistance in the ground circuit of the rear compartment occupant sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | -- |
13 | Repair the open or short to ground on the Ignition 0 Voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you correct the condition? | -- | Go to Step 17 | -- |
14 | Replace the rear compartment occupant sensor. Did you complete the replacement? | -- | Go to Step 17 | -- |
15 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 |
16 |
Important: When replacing the BCM refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | -- | Go to Step 17 | -- |
17 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
