Fog Lamp Indicator

WARNING: This page is about a different car, the 2017 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The fog lamp indicator gives an indication to the vehicle operator whenever the optional fog lamps are illuminated. This indicator is controlled by the Instrument Panel Cluster (IPC) circuit board based upon IPC programming and electronic messages received by the IPC from the Body Control Module (BCM) over the Controller Area Network (CAN) data bus.

The fog lamp indicator is completely controlled by the IPC logic circuit, and that logic will only allow this indicator to operate when the IPC receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the indicator will always be OFF when the ignition switch is in any position except ON or START. The indicator only illuminates when it is energized by the IPC logic circuit. The IPC will turn ON the fog lamp indicator for the following reasons:

Fog Indicator Lamp-On Message - Each time the cluster receives an electronic fog indicator lamp-ON message from the BCM indicating the fog lamp circuit is energized, the fog lamp indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the BCM, until the ignition switch is turned to the OFF position or until the exterior lamp load shedding (battery saver) timed interval expires, whichever occurs first.

The BCM continually monitors electronic exterior lighting switch status messages from the IPC to determine the appropriate outputs to the fog lamps. The BCM activates or deactivates the fog lamp circuit then sends the proper lamp-ON or lamp-OFF message back to the IPC. For further diagnosis of the fog lamp indicator or the IPC circuitry that controls the indicator. Refer to DIAGNOSIS AND TESTING .