Diagnostic Instructions

1. Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
2. Review Strategy Based Diagnosis for an overview of the diagnostic approach.
3. Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B3881 01: Tail Lamp Circuit Short to Battery

DTC B3881 02: Tail Lamp Circuit Short to Ground

DTC B3881 04: Tail Lamp Circuit Open

DTC B3882 01: Right Tail Lamp Circuit Short to Battery

DTC B3882 02: Right Tail Lamp Circuit Short to Ground

DTC B3882 04: Right Tail Lamp Circuit Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Tail Lamp	B3881 02	B3881 04	B3881 01	--
Right Tail Lamp	B3882 02	B3882 04	B3882 01	--

Circuit/System Description

The headlamp switch is supplied with ground at all times. When the headlamp switch is placed in either the park or low beam position, ground is applied to the Tail lamp signal circuit to the body control module (BCM). The BCM responds by applying battery voltage to the left and to the right tail lamp control circuits. This energizes the tail lamps.

Conditions for Running the DTC

B3881 01 or B3882 01

B3881 02, B3882 02, B3881 04 or B3882 04

The headlamp switch is in park or low beam position.

Conditions for Setting the DTC

B3881 01 or B3882 01

The BCM detects a short to voltage on the control circuit.

B3881 02 or B3882 02

The BCM detects a short to ground on the control circuit.

B3881 04 or B3882 04

The BCM detects an open control circuit.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, perform the appropriate Taillamp Command test. The appropriate tail lamp should be ON / OFF.

Circuit/System Testing

1. Ignition OFF, disconnect the appropriate harness connector at the tail lamp listed below:

•	E42L Tail lamp left

•	E42R Tail lamp right

2. Test for less than 5 Ω between the appropriate ground circuit harness connector terminal listed below and ground:

•	E42L Tail lamp left harness connector terminal F

•	E42R Tail lamp right harness connector terminal D

⇒	If greater than the specified value, test the appropriate ground circuit for an open / high resistance.

3. Connect a test lamp between the appropriate control circuit harness connector terminal listed below and ground :

•	E42L Tail lamp left harness connector terminal B

•	E42L Tail lamp left harness connector terminal E

•	E42R Tail lamp right harness connector terminal A

•	E42R Tail lamp right harness connector terminal B

4. Command the appropriate Taillamp Command test with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the appropriate control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module (BCM).

⇒	If the test lamp is always OFF, test the appropriate control circuit for a short to ground or an open / high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).

5. If all circuits test normal, test or replace the appropriate tail lamp.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.