Light Bar Lamp Indicator: Operation

WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.

The light bar lamp indicator gives an indication to the vehicle operator whenever the light bar lamps are illuminated. In certain markets where required, the high beam indicator also gives an indication when the optional light bar 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 Body Control Module (BCM) over the Programmable Communications Interface (PCI) data bus.

The light bar 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 light bar lamp indicator for the following reasons:

Light Bar Lamps-On Message - Each time the cluster receives a light bar lamps-on message from the BCM indicating the light bar lamps are turned On, the light bar lamp indicator will be illuminated. The indicator remains illuminated until the cluster receives a light bar lamps-off message from the BCM.
Actuator Test - Each time the cluster is put through the actuator test, the light bar 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 BCM continually monitors the light bar lamp switch to determine the appropriate outputs to the light bar lamp relay. The BCM then sends the proper light bar lamp-on and lamp-off messages to the instrument cluster. For further diagnosis of the light bar lamp indicator or the instrument cluster circuitry that controls the indicator, (Refer to ELECTRICAL/INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING) .

For proper diagnosis of the light bar lamp system, the BCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the light bar lamp indicator, a diagnostic scan tool is required. Refer to the appropriate diagnostic information.