Circuit/System Description

Daytime Running Lamps - with T4A 

The ambient light sensor is used to monitor outside lighting conditions. The body control module (BCM) provides a low reference ground and 5V reference signal to the ambient light sensor. Depending on outside lighting conditions, the ambient light sensor provides a voltage signal to the BCM that will vary between 0.2 and 4.9V. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lamps or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions, the BCM responds by applying battery voltage to the left and right headlamp low beam relay control circuits which energizes both headlamp low beam relays. With the headlamp low beam relays energized, the switch contacts close allowing battery voltage to flow to the daytime running lamp control circuits illuminating the left and right daytime running lamps. Any function or condition that turns on the headlamps will cancel daytime running lamps operation.

Daytime Running Lamps - with T4F 

The ambient light sensor is used to monitor outside lighting conditions. The body control module (BCM) provides a 5V reference signal to the ambient light sensor. Depending on outside lighting conditions, the ambient light sensor provides a voltage signal to the BCM that will vary between 0.2 and 4.9V. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lamps or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will command the daytime running lamps ON by applying voltage to the left and right daytime running lamp control circuits illuminating the daytime running lamps. Any function or condition that turns on the headlamps will cancel daytime running lamps operation.