Circuit Description
The rear fog lamp switch circuit provides a direct battery input to the BCM when the switch is pressed. This input allows the BCM to detect a rear fog lamps switch ON or OFF request. If the BCM detects battery voltage on the rear fog lamp circuit (CKT 187) when the rear lamps are OFF, the BCM will turn ON the lamps by energizing the rear fog lamp relay. If the BCM detects battery voltage after the rear fog lamps ON command, the BCM will turn OFF the lamps. The BCM monitors CKT 187 in order to determine how long the voltage has been applied. If the voltage is applied for longer than expected, a malfunction is present and a DTC will set.
Conditions for Setting the DTC
The BCM detects battery voltage on CKT 187 for longer than 60 seconds.
Action Taken When the DTC Sets
| • | Stores a DTC B2408 in the BCM memory. |
| • | No driver warning message will be displayed for this DTC. |
Conditions for Clearing the DTC
| • | The BCM no longer detects battery voltage on CKT 187 for longer than 60 seconds. |
| • | A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present. |
| • | Use the IPC clearing DTCs feature. |
| • | Use a scan tool. |
Diagnostic Aids
| • | The following conditions may cause an intermittent malfunction: |
| - | There is an intermittent short to voltage in CKT 187. |
| - | The rear fog lamp switch is internally shorted to voltage or is sticking. |
| - | The rear fog lamp switch is pressed for longer than 60 seconds. |
| • | If CKT 187 is shorted to voltage, the rear fog lamps will remain ON or OFF at all times depending on whether the lamps were ON or OFF when the short occurred. If the short occurred when the lamps were ON, the lamps will remain OFF at all times. If the short occurred when the lamps were OFF, the lamps will remain ON at all times. The BCM will remember whether the lamps were ON or OFF even if the ignition is switched OFF. |
| • | If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Refer to Intermittents and Poor Connections Diagnosis . |
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This test determines the status of the rear fog lamp switch using a scan tool. The scan tool will display the rear fog lamp switch status as ACTIVE (button pressed) and INACTIVE (button released).
-
This test checks if the rear fog lamp switch is shorted to ground or stuck. If the rear fog lamp switch status changes from ACTIVE to INACTIVE when the rear fog lamp switch is disconnected, then the rear fog lamp switch must be replaced.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Were you sent here from the BCM Diagnostic System Check? | -- | ||
Does the scan tool display rear fog lamp switch status as ACTIVE? | -- | |||
Does the scan tool display rear fog lamp switch status as ACTIVE? | -- | |||
4 | Check for a short to voltage in CKT 187. Was a problem found and repaired? | -- | ||
5 | Replace the rear fog lamp switch. Refer to Fog Lamp Switch Replacement in Lighting Systems. Is the replacement complete? | -- | -- | |
6 |
Is the replacement complete? | -- | -- | |
7 | Check the rear fog lamp switch circuit for an intermittent malfunction. Refer to Diagnostic Aids. Was a problem found and repaired? | -- | ||
8 |
Does DTC B2408 set as current? | -- | System OK | |
9 |
Is the repair complete? | -- | -- |
