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 Descriptor
DTC B3890 02: Trailer Backup Lamps Circuit Short to GroundDTC B3890 04: Trailer Backup Lamps Circuit Open
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Trailer Backup Lamps | 3890 02 | 3890 04 | -- | -- |
Circuit/System Description
When the transmission is placed in the reverse position, the engine control module (ECM) sends a serial data message to the body control module (BCM). The message indicates that the gear selector is in the reverse position. The BCM sends this message to the trailer lighting converter. The trailer lighting converter then applies a voltage to the trailer backup lamps through there supply circuit.
Conditions for Running the DTC
B3890 02 or B3890 04
The appropriate trailer backup lamp signal is active
Conditions for Setting the DTC
B3890 02
The trailer lighting converter detects a short to ground on the control circuit.
B3890 04
The trailer lighting converter detects an open control circuit.
Conditions for Clearing the DTC
The condition for setting the DTC is not longer present.
Action Taken When the DTC Sets
The appropriate trailer backup lamp is inoperative.
Reference Information
Schematic Reference
Trailer Connector/Provision Schematics
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, perform the Trailer Backup Lamps test. The trailer backup lamp should be ON/OFF
Circuit/System Testing
- Ignition OFF, test for less than 5 Ω between the X88 Trailer Connector terminal 3, 11, 13 and ground.
- Connect a test lamp between the X88 Trailer Connector terminal 8 and ground.
- Command the Trailer Backup Lamps Active / Inactive test with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all the circuits test normal, test the backup lamp circuit at the trailer.
| ⇒ | If greater than the specified value, test the appropriate ground circuit for an open/high resistance. |
| ⇒ | 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 Converter. |
| ⇒ | 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 Converter. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for trailer lighting converter replacement, setup and programming
