Circuit Description
The body control module (BCM) monitors the front fog lamp switch signal circuit in order to determine when the fog lamp relay is to be energized. When the BCM senses that the front fog lamp switch signal circuit is low momentarily by pressing the fog lamp switch, the BCM energizes the fog lamp relay by grounding the fog lamp relay control circuit.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2527 Front Fog Lamps Circuit Low
Conditions for Running the DTC
| • | The battery voltage must be between 9.0-16.0 volts. |
| • | Ignition switch in the RUN position. |
| • | Fog lamp switch ON. |
Conditions for Setting the DTC
When the front fog lamp switch signal circuit is shorted to ground for approximately 3 minutes.
Action Taken When the DTC Sets
The fog lamps will not operate.
Conditions for Clearing the MIL/DTC
| • | This DTC will clear on current status after the condition for setting the fault is corrected. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
| • | History and current DTCs can be cleared using a scan tool. |
Diagnostic Aids
| • | Test the fog lamp switch for sticking in the ON position. |
| • | Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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OFF is the normal state of the switch before activation.
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OFF is the normal state of the switch before activation.
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This step tests for a short to ground on the signal circuit.
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After replacement of the BCM you must calibrate the new module for proper operation.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Fog Lights Schematics Connector End View Reference: Lighting Systems Connector End Views or Computer/Integrating Systems Connector End Views in Computer/Integrating Systems | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the scan tool display OFF? | OFF/ON | Go to Step 3 | Go to Step 4 | |
3 |
Does the front fog lamp switch parameter change state? | -- | Go to Diagnostic Aids | Go to Step 4 |
Does the scan tool display OFF? | OFF/ON | Go to Step 7 | Go to Step 5 | |
Test the signal circuit of the front fog lamp switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 | |
6 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
7 | Inspect for poor connections at the harness connector of the front fog lamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 10 | -- | |
9 | Replace the front fog lamp switch. Refer to Headlamp Switch Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
