Sun Load Sensor Failure Trouble Code

NAME OF CODE
Sun Load Sensor Failure

WHEN MONITORED
With ignition on

SET CONDITION
BCM senses an abnormally low voltage on its input.

THEORY OF OPERATION
The sun load sensor is a reverse-biased diode for which the BCM provides a 5V pull-up. The BCM has two different pull-up resistors which bias the diode differently for use with the Automatic Temperature Control (ATC) system and the Auto Headlamp (Ultralight) system (even if the vehicle is not equipped with Ultralight). As light shines on the diode, a current is produced in it, resulting in the voltage read by the BCM. With no current flowing (which occurs when it is dark), the BCM will read 5V. However even in the brightest light the voltage on this pin will not fall below 0.313V without a failure when it is biased for ATC, which will result in this fault.

PROBABLE CAUSES
- Wiring short to ground
- Failed sensor
- Failed BCM