Circuit Description
The ambient light sensor circuit provides an input to the BCM for DRLand automatic headlight functions. This input allows the BCM to activate or deactivate DRL and automatic headlamps with different ambient light levels. The BCM supplies a DRL ambient light sensor low reference circuit and a signal circuit to theambient light sensor. The BCM will detect high voltage on the ambient lightsensor signal circuit when ambient light is high, and low voltage when ambient light is low. The BCM monitors the ambient light sensor voltageat the signal circuit and determines if the voltage is within range. Ifthe voltage is not within range, a malfunction is present and a DTC willset.
Conditions for Setting the DTC
| • | A short to voltage in the ambient light sensor circuit. |
| • | A short to voltage in the DRL ambient light sensor low reference. |
| • | Condition must be present for 2 seconds. |
Action Taken When the DTC Sets
| • | Stores a DTC B2648 in the BCM memory. |
| • | The automatic headlamps and park lamps will remain ON. |
Conditions for Clearing the DTC
| • | The BCM no longer detects a short to voltage in the ambient lightsensor circuit. |
| • | The BCM no longer detects a short to voltage in the DRL ambient light sensor low reference circuit. |
| • | A history DTC will clear after 50 consecutive ignitioncycles if the condition for the malfunction is no longer present. |
| • | Use the IPC clearing DTCs feature. |
| • | The BCM receives the Clear Code command from the scan tool. |
Diagnostic Aids
| • | The following conditions may cause an intermittent malfunction: |
| - | An intermittent short to voltage in the ambient light sensor signal circuit. |
| - | An intermittent short to voltage in the ambient light sensor reference circuit. |
| • | If the ambient light sensor circuit is open or shorted (to groundor voltage), the BCM will command the automatic headlamps and park lamps ON. If the ignition is cycled the BCM will retest for any malfunctions in the ambient light sensor circuit and if a malfunction is current the BCM will activate the automatic. |
| • | If the DTC is a history DTC, the problem may be intermittent.Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
-
Tests ambient light sensor data using a scan tool.
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Tests the ambient light sensor data with the sensor disconnected. The scan tool will display ambient light sensor voltage as 0 volts with the sensor disconnected.
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Tests the ambient light sensor data with a jumper wire between the reference and signal circuit. The scan tool will display ambient light sensor voltage between 3.5-4.5 voltswith the sensor jumpered.
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Tests for a short to voltage in the DRL ambient light sensor low reference circuit.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Master Electrical Component List | ||||
1 | Did you perform the Lighting System Diagnostic System Check? | -- | Go to Step 2 | |
Does the scan tool indicate that the DRL Ambient Light Sensor parameter is within the specified range? | 0.1-2.5 V | Go to Diagnostic Aids | Go to Step 3 | |
Does the scan tool indicate that the DRL Ambient Light Sensor parameter is less than the specified value? | 0.1 V | Go to Step 4 | Go to Step 9 | |
Does the scan tool indicate that the DRL Ambient Light Sensor parameter is greater than the specified value? | 3.5 V | Go to Step 5 | Go to Step 7 | |
Does the voltage measure less than the specified value? | 5.0 V | Go to Step 10 | Go to Step 6 | |
6 | Test the DRL ambient light sensor low reference circuit of the ambient light sensor for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
7 | Test the DRL ambient light sensor low reference circuit of the ambient light sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 8 |
8 | Test the signal circuit of the ambient light sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
9 | Test the signal circuit of the ambient light sensor for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
10 | Inspect for poor connections at the harness connector of the ambient light sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 |
11 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 |
12 | Replace the ambient light sensor. Refer to Daytime Running Lamp (DRL) Ambient Light Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 |
Important: Perform the BCM reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
