Automatic Headlamps

WARNING: This page is about a different car, the 2015 RAM 3500 HD and 2015 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The automatic headlamp system includes the headlamp switch, the Body Control Module (BCM) (also known as the Common Body Controller/CBC), and the Twilight Sensor on the top of the instrument panel.

The Twilight Sensor provides an ambient light level input to the A/C - heater control whenever the ignition switch is in the ON position. The sensor is powered on by the HVAC control module. The A/C - heater control responds to this input by sending the appropriate electronic light level messages to the BCM over the Controller Area Network (CAN) data bus. When the AUTO (Automatic) position is selected with the headlamp switch, the BCM receives a hard wired multiplex input from the headlamp switch. The BCM also receives electronic messages over the CAN data bus from the PCM indicating the engine is running.

NOTE:

If the truck is equipped with Light Rain Sensing Module (LRSM) and tunnel detection feature is enabled then the input for automatic headlamps is taken from the LRSM.

The BCM responds to these input conditions by automatically controlling the selected headlamp bulbs or lighting elements through the right and left low or high beam driver circuits to illuminate the headlamps. The BCM also remembers which beams (low or high) were selected when the headlamps were last turned OFF, and energizes those beams and lamps again the next time it turns the headlamps ON.

Headlights On With Wipers - When this feature is active, the headlights will turn on approximately 10 seconds after the wipers are turned on if the headlight switch is placed in the AUTO position. In addition, the headlights will turn off when the wipers are turned off, if they were turned on by this feature. The feature is programmable on/off through the Electronic Vehicle Information Center (EVIC) or through the Radio Receiver Module (RRM) screen display.