DTC B3891
Diagnostic Instructions
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
|
3891 02
|
3891 04
|
-
|
-
|
|
| |
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 applies voltage to the trailer fog lamps
through their 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
Trailer Connector/Provision Schematics
Connector End View Reference
Component Connector End Views
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 Fog Lamp(s) test. The trailer
fog lamps should be ON/OFF
Circuit/System Testing
Trailer Fog Lamp Malfunction RPO VQ9
| 1. |
Ignition OFF, test for less
than 5 Ω between the X88 Trailer Connector terminal 3, 11, 13
and ground. |
| ⇒ |
If greater than the specified value, test the
appropriate ground circuit for an open/high resistance. |
| 2. |
Connect a test lamp between
the X88 Trailer Connector terminal 2 and ground. |
| 3. |
Command the Trailer Fog
Lamp(s) test with a scan tool. The test lamp should turn ON and OFF
when changing between the commanded states. |
| ⇒ |
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. |
| ⇒ |
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. |
| 4. |
If all the circuits test
normal, test the fog lamps circuit at the trailer. |
Trailer Fog Lamp Malfunction RPO D8G
| 1. |
Ignition OFF, remove the
appropriate bulb and inspect. |
| ⇒ |
If bulb is faulty, replace bulb. |
| 2. |
Ignition OFF, remove the bulb
of the appropriate component listed below: |
| |
• |
E29LR Fog Lamp - Left
Rear |
| |
• |
E29RR Fog Lamp - Right
Rear |
| 3. |
Test for less than 5 Ω
between the ground circuit harness connector wiring color WH and
ground. |
| ⇒ |
If greater than the specified value, test the
appropriate ground circuit for an open/high resistance. |
| 4. |
Connect a test lamp between
the appropriate control circuit terminal listed below and
ground: |
| |
• |
E29LR Fog Lamp - Left Rear
wiring color dark BU |
| |
• |
E29RR Fog Lamp - Right Rear
wiring color GY |
| 5. |
Command the Trailer Fog
Lamp(s) test with a scan tool. The test lamp should turn ON and OFF
when changing between the commanded states. |
| ⇒ |
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. |
| ⇒ |
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. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
Control Module References for trailer lighting converter
replacement, setup, and programming
|
