DTC B108E

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. DTC Descriptors DTC B108E Ambient Light Sensor Signal Refer to Symptom Byte List for symptom byte information. Diagnostic Fault Information

Circuit	Circuit Function	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performan
278	Signal	B108E 00	B108E 00	B108E 00	—
407	Low Reference	1	B108E 00	1	—
1. Ambient Light Sensor Malfunction

Circuit/System Description The B10D Sun Load and Ambient Light and Security Indicator Sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 volts depending on outside lighting conditions. The K9 Body Control Module (BCM) provides signal circuit 278 and low reference circuit 407 to the ambient light sensor. 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 mode is in the AUTO position. In daylight conditions the BCM will request the daytime running lamps ON through a serial data message to the K219 Lighting Control Module. During low light conditions the BCM will request the low beam headlamps ON through a serial data message to the lighting control module. Conditions for Running the DTC Battery voltage must be between 9-16 V. Conditions for Setting the DTC The BCM detects a circuit fault on the ambient light sensor signal circuit 278. Actions Taken When the DTC Sets The BCM defaults to low light status and commands the low beam headlamps ON. Conditions for Clearing the DTC The condition responsible for setting the DTC no longer exists. A history DTC will clear once 40 consecutive malfunction-free ignition cycles have occurred. Reference Information Schematic Reference Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference Master Electrical Component List Description and Operation Exterior Lighting Systems Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Testing

1. Ignition/vehicle OFF, disconnect the B10D Sun Load and Ambient Light and Security Indicator Sensor.
2. Ignition/vehicle ON, verify a test lamp illuminates between low reference terminal 6 and B+. ⇒ If the test lamp does not illuminate 2.1. Test circuit 407 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 2.2. Replace the K9 Body Control Module. ⇓ If the test lamp illuminates
3. Test for 4.8 V – 5.2 V between signal circuit terminal 3 and ground. ⇒ If less than 4.8 V 3.1. Test circuit 278 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 3.2. Test circuit 278 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 3.3. Replace the K9 Body Control Module. ⇒ If greater than 5.2 V 3.1. Test circuit 278 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 3.2. Replace the K9 Body Control Module. ⇓ If between 4.8 V – 5.2 V
4. Replace the B10D Sun Load and Ambient Light and Security Indicator Sensor. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup