PRE-RELEASE
DTC B2540
| DTC B2540 |
| 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 B2540 02
Rear Fog Lamps Control Circuit Short to Ground
DTC B2540 04
Rear Fog Lamps Control Circuit Open
| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
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Rear Fog Lamps Control
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B2540 02
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B2540 04
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1
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1. Rear fog lamp always ON
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| Circuit/System Description |
The body control module (BCM) energizes the rear fog lamp by applying voltage to the rear fog lamp control circuit. When the rear fog lamp control circuit is energized the rear fog lamp is illuminated.
| Conditions for Running the DTC |
Rear fog lamp activated.
| Conditions for Setting the DTC |
B2540 02
The BCM detects a short to ground on the control circuit.B2540 04
The BCM detects an open control circuit.| Action Taken When the DTC Sets |
The appropriate fog lamp is inoperative.
| Conditions for Clearing the DTC |
The condition for setting the DTC is no longer present.
| Reference Information |
Schematic Reference
Fog Lights 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 Rear Fog Lamp(s) Relay test. The rear fog lamp should be ON/OFF when changing between the commanded states.
| Circuit/System Testing |
| 1. |
Ignition OFF, disconnect the harness connector at the E29R Fog Lamp - Rear.
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| 2. |
Test for less than 5 Ω between the E29R Fog Lamp - Rear harness connector terminal A and ground:
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| 3. |
If greater than the specified value, test the appropriate ground circuit for an open circuit/high resistance.
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Connect a test lamp between the E29R Fog Lamp - Rear harness connector terminal B and ground.
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Ignition ON, perform the Rear Fog Lamps Relay Command test. The rear fog lamp should be ON/OFF when changing between the commanded states.
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If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
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If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K9 Body Control Module.
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| 8. |
If all circuits test normal, test or replace the E29R Fog Lamp - Rear.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Rear Fog Lamp Replacement
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Control Module References
for information on BCM replacement, setup, and programming
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