Service Information

Cruze

DTC B3891

Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B3891 02: Trailer Fog Lamps Circuit Short to Ground

DTC B3891 04: Trailer Fog Lamps Circuit Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Trailer Fog Lamps Control	B3891 02	B3891 04	1	--
1. Trailer Fog Lamps Always ON

The trailer lighting control module will receive a serial data message from the body control module (BCM) indicating that the vehicle rear fog lamps have been activated. The trailer lighting control module will then apply system voltage to the trailer fog lamps through their respective voltage supply circuits.

Conditions for Running the DTC

When the trailer fog lamps are turned on.

Conditions for Setting the DTC

B3891 02

The trailer lighting control module detects a short to ground on the trailer fog lamp control circuit.

B3891 04

The trailer lighting control module detects an open/high resistance on the trailer fog lamp control circuit.

Action Taken When the DTC Sets

The trailer fog lamps will be inoperative.

Conditions for Clearing the DTC

•	The DTC will be current for as long as the fault is present.

•	When the fault is no longer present, the DTC will be a history DTC.

•	A history DTC will clear after 40 ignition cycles.

Reference Information

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the function of the trailer fog lamps while commanding the Trailer Fog Lamp ON and OFF with a scan tool. The trailer fog lamps should turn ON and OFF while changing between the commanded states.

Circuit/System Testing

Ignition OFF, test for less than 5 Ω between the X88 Trailer Connector terminal 3, 11, 13 and ground.

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

Connect a test lamp between the X88 Trailer Connector terminal 2 and ground.
Command the Trailer Fog Lamps Active/Inactive 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 signal circuit for a short to voltage. If the circuit tests normal, replace the K68 Trailer Lighting Control Module.

⇒	If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K68 Trailer Lighting Control Module.

If all the circuits test normal, test the fog lamps circuit at the trailer.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for trailer lighting control module replacement, programming and setup