DTC B3891
DTC B3891 |
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 B3891 02
Trailer Fog Lamps Circuit Short to Ground
DTC B3891 04
Trailer Fog Lamps Circuit Open
Diagnostic Fault Information |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
Trailer Fog Lamps Control
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3891 02
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3891 04
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-
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-
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Circuit/System Description |
The front fog lamp switch signal circuit is grounded momentarily by pressing the front fog lamp switch. The body control module (BCM) sends this message to the trailer lighting converter. The trailer lighting converter then applies a voltage to the trailer fog lamps through there supply circuit.
Conditions for Running the DTC |
B3891 02 or B3891 04
The appropriate trailer fog lamps signal is active.Conditions for Setting the DTC |
B3891 02
The trailer lighting converter detects a short to ground on the control circuit.B3891 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 fog lamp is inoperative.
Reference Information |
Schematic Reference
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 Fog Lamp(s) test. The trailer fog lamps 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 2 and ground.
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4. |
Command the Trailer Fog Lamp(s) 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 fog lamps 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