PRE-RELEASE
DTC B3890
| DTC B3890 |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
has overviews of all diagnostic categories.
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| DTC Descriptors |
DTC B3890 02
Trailer Backup Lamps Circuit Short to Ground
DTC B3890 04
Trailer Backup Lamps Circuit Open
| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
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Trailer Backup Lamps Control
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3890 02
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3890 04
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| Circuit/System Description |
When the transmission is placed in reverse gear, 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 no 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
Component Connector End Views
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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Scan Tool Reference
Control Module References for information on diagnostic tools
| Circuit/System Verification |
Ignition ON, perform the Trailer Backup Lamps test. The trailer backup lamp should be ON/OFF.
| Circuit/System Testing |
| 1. |
Ignition OFF, test for less than 5 Ω between the X88 Trailer Connector terminal 3, 11, 13 and ground.
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| 2. |
If greater than the specified value, test the appropriate ground circuit for an open circuit/high resistance.
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| 3. |
Connect a test lamp between the X88 Trailer Connector terminal 8 and ground.
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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.
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| 5. |
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 Control Module.
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| 6. |
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 Control Module.
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| 7. |
If all the circuits test normal, test the backup lamp circuit at the trailer.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for trailer lighting converter replacement, setup and programming
