GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Terrain 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B3888

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

DTC Descriptors

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

DTC B3888 05: Trailer Right Turn Signal Circuit - Short to Battery or Open

Circuit/System Description

When the right turn signal switch is placed in the ON position, ground is applied to the auxiliary body control module (XBCM) through the turn signal lamp switch circuit. The XBCM then applies voltage on the trailer turn signal lamp circuit to the trailer right turn signal lamp.

Conditions for Running the DTC
    • The ignition is ON.
    • The right turn signal lamps must be ON and the right turn signal lamp must be commanded ON.

Conditions for Setting the DTC

The body control module (BCM) detects an open, short to ground, or short to voltage on the trailer right turn signal lamp circuit while trying to apply a voltage to the circuit.

Action Taken When the DTC Sets

The trailer right turn signal lamp does not illuminate.

Conditions for Clearing the DTC
    • The conditions for setting the DTC are no longer present.
    • A history DTC clears after 100 malfunction-free ignition cycles.
    • The BCM receives the clear code command from the scan tool.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Output Controls
    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Ignition ON, activate with a scan tool the Trailer Right Turn Signal Lamp switch, trailer right turn signal lamp should illuminate.

Circuit/System Testing
  1. Inspect the trailer right turn signal lamp bulb for an open or shorted filament.
    2. ⇒ If the bulb is inoperable, replace the bulb.
  2. Turn signal lamp switch OFF. Clear the DTC. Test the trailer right turn signal lamp circuit for a short to voltage, short to ground, an open, or high resistance.
    3. ⇒If all circuits/connections test normal, replace the XBCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for XBCM replacement, setup, and programming