Circuit Description
The ambient light sensor indicates the light level to control the automatic headlamps and park lamps. The body control module (BCM) provides a 5-volt reference signal to the light sensor through the ambient light sensor signal circuit. The BCM receives the modified voltage from the ambient light sensor through the ambient light sensor low reference circuit. A low voltage under 1.5 volt, signals a dark condition to the BCM and vice versa.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2647 Ambient Light Sensor Circuit Low
Conditions for Running the DTC
The ignition switch is in the ON position.
Conditions for Setting the DTC
Any of the following conditions will set this DTC:
| • | The ambient light sensor signal reference circuit is open for 5 seconds. |
| • | The ambient light sensor signal reference circuit is shorted to ground for 5 seconds. |
| • | The ambient light sensor signal return circuit is open for 5 seconds. |
| • | The ambient light sensor signal return circuit is shorted to ground for 5 seconds. |
Action Taken When the DTC Sets
The headlamps and park lamps are always illuminated with the ignition ON.
Conditions for Clearing the DTC
| • | The conditions for setting the DTC are no longer present. |
| • | A history DTC clears after 100 malfunction free ignition cycles. |
| • | The BCM receives the clear code command from the scan tool. |
Diagnostic Aids
If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
The normal operating voltage of the ambient light sensor (photocell) is 0.5-4.5 volts.
-
This step determines if there is a problem with the signal circuit of the ambient light sensor.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the scan tool indicate that the PHOTOCELL VOLTAGE parameter is within the specified range? | 0.5-4.5 V | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
Does the test lamp illuminate? | -- | Go to Step 4 | Go to Step 5 | |
4 |
Does the scan tool indicate that the PHOTOCELL VOLTAGE parameter is within the specified range? | 4.5-5.0 V | Go to Step 7 | Go to Step 6 |
5 | Test the signal circuit of the ambient light sensor for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 |
6 | Test the low reference circuit of the ambient light sensor for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 |
7 | 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 11 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the body control module (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 11 | Go to Step 10 |
9 | Replace the ambient light sensor. Did you complete the replacement? | -- | Go to Step 11 | -- |
10 | Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | -- |
11 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
