Patriot 4WD L4-2.4L VIN W (2007)
Fog/Driving Lamp Indicator: Description and Operation
Rear Fog Lamp Indicator
Description
DESCRIPTION
A rear fog lamp indicator is standard equipment on all instrument clusters for certain markets where rear fog lamps are available. However, on vehicles
not equipped with the optional rear fog lamps, this indicator is electronically disabled. This indicator is located above the engine coolant temperature
gauge on the cluster overlay, to the right of the tachometer.
The rear fog lamp indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for Rear Fog Light in the opaque layer
of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. An
amber Light Emitting Diode (LED) behind the cutout in the opaque layer of the overlay causes the indicator to appear in amber through the translucent
outer layer of the overlay when it is illuminated from behind by the LED, which is soldered onto the instrument cluster electronic circuit board.
The rear fog lamp indicator is serviced as a unit with the instrument cluster.
Operation
OPERATION
The rear fog lamp indicator gives an indication to the vehicle operator whenever the rear fog lamps are illuminated. This indicator is controlled by a
transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Totally
Integrated Power Module (TIPM) over the Controller Area Network (CAN) data bus.
The rear fog lamp indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will allow this
indicator to operate whenever the instrument cluster receives a battery current input on the fused B(+) circuit. Therefore, the LED can be illuminated
regardless of the ignition switch position. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The
instrument cluster will turn ON the rear fog lamp indicator for the following reasons:
-
Rear Fog Indicator Lamp-On Message - Each time the cluster receives an electronic rear fog indicator lamp-ON message from the TIPM
indicating the rear fog lamps are turned ON, the rear fog lamp indicator will be illuminated. The indicator remains illuminated until the cluster
receives a lamp-OFF message from the TIPM, or until the exterior lamp load shedding (battery saver) timed interval expires, whichever occurs
first.
-
Actuator Test - Each time the cluster is put through the actuator test, the rear fog lamp indicator will be turned ON, then OFF again during the
bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.
The TIPM continually monitors electronic exterior lighting request messages from the ElectroMechanical Instrument Cluster (EMIC) to determine the
appropriate outputs to the rear fog lamps. The TIPM activates or deactivates the rear fog lamps then sends the proper lamp-ON or lamp-OFF message
back to the EMIC.
For proper diagnosis of the rear fog lamp system, the TIPM, the EMIC, the CAN data bus or the electronic communication related to rear fog lamp
indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.
