B3890

DTC B3890

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 B3890 02
- Trailer Backup Lamps Circuit Short to Ground

DTC B3890 04
- Trailer Backup Lamps Circuit Open

Diagnostic Fault Information





Circuit/System Description

The trailer brake control module will receive a serial data message from the BCM indicating that the vehicle backup lamps have been activated. The trailer brake control module will then apply system voltage to the trailer backup lamps through their respective voltage supply circuits.

Conditions for Running the DTC

When the trailer backup lamps are turned on.

Conditions for Setting the DTC

B3890 02

The trailer brake control module detects a short to ground on the trailer backup lamp control circuit.

B3890 04

The trailer brake control module detects an open/ high resistance on the trailer backup lamp control circuit.

Action Taken When the DTC Sets

The trailer backup 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
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 trailer backup lamps while commanding the Trailer Backup Lamp ON and OFF with a scan tool. The trailer backup lamps should turn ON and OFF while changing between the commanded states.

Circuit/System Testing

1. Ignition OFF, disconnect the X1 harness connector at the K68 trailer lighting control module.
2. Test for infinite resistance between the control circuit terminal 7 and ground.

• If less than the specified value, test the control circuit for a short to ground. If the circuit tests normal, replace the X88 trailer connector.

3. Test for less than 1 ohm between the control circuit terminal 7 at the K68 trailer lighting control module and control circuit terminal 8 at the X88 trailer connector.

• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the X88 trailer connector.

4. If all the circuits test normal, replace the K68 trailer lighting control module.

Repair Instructions

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

Control Module References (Programming and Relearning) for the trailer brake control module replacement, setup and programming