DTC B119: Twilight Photocell Circuit: Description

The twilight sensor uses a photocell to control signal voltage to BCM. The BCM applies a voltage on CKT 278 to sensor. When sensor detects darkness its resistance is high, therefore BCM will see a high signal voltage. As sensor detects light its resistance becomes less and signal voltage is pulled low through ground, CKT 736. This signal voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).