Without U4G

DTC B3887 or B3888 (Without U4G)

Diagnostic Instructions

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

DTC Descriptors
DTC B3887 02
- Trailer Left Turn Signal Circuit Short to Ground

DTC B3887 04
- Trailer Left Turn Signal Circuit Open

DTC B3888 02
- Trailer Right Turn Signal Circuit Short to Ground

DTC B3888 04
- Trailer Right Turn Signal Circuit Open

Diagnostic Fault Information





Circuit/System Description

When the appropriate turn signals are activated, the BCM will apply a pulsating ground to the appropriate trailer stop/turn signal lamp relay.

Conditions for Running the DTC

The system voltage is 9-16 V.

Conditions for Setting the DTC

B3887 02 or B3888 02

The BCM detects a short to ground on the appropriate trailer turn signal control circuit.

B3887 04 or B3888 04

The BCM detects an open/high resistance on the appropriate trailer turn signal control circuit

Action Taken When the DTC Sets

The appropriate trailer turn signal lamp 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
Schematic Reference

Trailer Connector/Provision Schematics (Trailer Connector/Provision Schematics)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Verification

Ignition ON, observe the function of the left trailer turn signal lamp and the right trailer turn signal lamp while commanding the Left Trailer Turn Signal Lamp and the Right Trailer Turn Signal Lamp ON and OFF with a scan tool. The left trailer turn signal lamp and the right trailer turn signal lamp should turn ON and OFF while changing between the commanded states.

Circuit/System Testing

1. Ignition OFF, disconnect the X5 harness connector at the K9 BCM.
2. Ignition ON, test for greater than 10 V between the control circuit terminal listed below and ground:

* Right trailer turn signal lamp control terminal 17
* Left trailer turn signal lamp control terminal 8

• If less than the specified value, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the X50 A fuse block-underhood.

3. If all the circuits test normal, replace the K9 BCM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Fuse Block Replacement (Fuse Block Replacement)
* Control Module References (Programming and Relearning)for BCM replacement, programming and setup