Code B119 - Twilight Photocell Circuit: Notes

The twilight sensor uses a photocell to control the signal voltage to the BCM. The BCM applies a voltage on circuit 278 to the sensor. When the sensor detects darkness its resistance is high, therefore the BCM will see a high signal voltage. As the sensor detects light its resistance becomes less and the signal voltage is pulled low through the ground, circuit 736. This signal voltage will vary between 5V (open circuit) and 0V (shorted circuit.)

Code B119 will set if the ignition is on and the signal voltage indicates more the 94 percent (open circuit) or less than 6 percent (shorted circuit). During the time the failure is present a substitute light reading (indicating darkness) will be implemented to allow continued operation of the headlamps. The measure of light reading BD44 will display the actual sensor reading.

1. BCM data value BD44 displays light level. The normal range is from 6-94 percent.
2. Check to see if the open circuit reading is due to the circuit or the sensor. If the open circuit reading changes to a shorted circuit reading after jumpering the sensor terminals, the BCM and wiring are okay.
3. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.
4. Check to see if the shorted circuit reading is due to the circuit on the sensor. If the shorted circuit reading changes to an open circuit reading after disconnecting the sensor, the BCM and wiring are okay.