B3887
DTC B3887 or B3888
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 01
-
Trailer Left Turn Signal Circuit Short to Voltage
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
Diagnostic Fault Information
Circuit/System Description
Ground is applied at all times to the turn signal/multifunction switch. When the turn signal/multifunction switch is placed in either the turn right or turn left position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. The BCM then applies a voltage to the appropriate trailer turn signal lamps through their respective relays.
Conditions for Running the DTC
The appropriate trailer turn signal is active.
Conditions for Setting the DTC
B3887 01
The BCM detects a short to voltage on the control circuits.
B3887 02 or B3888 02
The BCM detects a short to ground on the control circuit.
B3887 04
The BCM detects an open control circuit.
Action Taken When the DTC Sets
The appropriate trailer turn signal lamp is inoperative.
Conditions for Clearing the DTC
The condition for setting the DTC is not longer present.
Action Taken When the DTC Sets
The appropriate trailer turn signal lamp is inoperative.
Reference Information
Schematic Reference
Trailer Connector/Provision Schematics Trailer Connector/Provision Schematics
Connector End View Reference
Component Connector End Views Sunshade - Left Front
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, turn the trailer turn signal lamps ON and OFF by turning the turn signal/multi-function switch between the left turn and right turn positions. The trailer turn signal lamp should turn ON and OFF when changing between the selected states.
Circuit/System Testing
1. Ignition OFF, disconnect the X2 harness connector at the X50A underhood fuse block.
2. Connect a test lamp between the control circuit terminal listed below and B+.
* Trailer Stop/Turn Lamp Right - Terminal A7
* Trailer Stop/Turn Lamp Left - Terminal A6
3. Switch the turn signal/multi-function switch between the left turn and right turn positions. The test lamp should turn ON and OFF when changing between the selected states.
• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace K9 BCM.
4. Ignition OFF, connect the X2 harness connector at the X50A underhood fuse block.
5. Test for less than 5 ohms between the X88 Trailer Connector ground circuit terminal D and ground
• If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between the control circuit terminal listed below and ground.
* Trailer Stop/Turn Lamp Right - Terminal C
* Trailer Stop/Turn Lamp Left - Terminal B
7. Switch the turn signal/multi-function switch between the left turn and right turn positions. The test lamp should turn ON and OFF when changing between the selected states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the X88 Trailer Connector.
• If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the X88 Trailer Connector.
• If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the X88 Trailer Connector.
8. If all circuits test normal, test or replace the X50A underhood fuse block.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Accessory Wiring Junction Block Replacement Accessory Wiring Junction Block Replacement
* Control Module References Programming and Relearning for trailer lighting converter replacement, setup and programming