B1A85 Code: Meaning, Causes, and Symptoms | OBD2 Codes

B1A85 – Ambient Light Sensor


B1A85 Possible Symptoms


Engine Light ON (or Service Engine Soon Warning Light)


B1A85 Possible Causes


Faulty Ambient Light Sensor,Ambient Light Sensor harness is open or shorted,Ambient Light Sensor circuit poor electrical connection,Faulty Steering Column Control Module (SCCM),Faulty Body Control Module (BCM)


B1A85 Description


The Steering Column Control Module (SCCM) sends voltage signals to the headlamp switch through the headlamp switch input circuits (off, parking lamps, headlamps, autolamps). At any given time, the headlamp switch routes one of the input circuits to ground, indicating the headlamp switch position to the SCCM . The SCCM sends the status of the headlamp switch position to the Body Control Module (BCM) over the High Speed Controller Area Network (HS-CAN). The autolamp feature is enabled when the BCM receives a message from the SCCM indicating the headlamp switch in the AUTOLAMPS ON position. When the BCM enables the autolamps feature, the BCM monitors the light sensor input. The light sensor determines the amount of light based on the input received from the ambient lighting conditions. When the ambient level has reached a point (determined by the internal programming of the BCM ), the BCM provides voltage to the exterior lamps. If the SCCM detects multiple or no active headlamp switch inputs, it sends a message to the BCM to indicate a fault with the headlamp switch input.