Circuit Description
The body control module (BCM) turns on the automatic lighting control (ALC) relay when the ambient light sensor senses a dark condition. Battery positive voltage is supplied to the ALC relay at all times through the LH HDLP fuse. The BCM grounds the ALC relay control circuit in order to activate the relay.
Conditions for Running the DTC
| • | The ignition switch is in the ON position. |
| • | The ambient light sensor senses a light condition (ALC headlamps off). |
Conditions for Setting the DTC
Either of the following conditions will set this DTC:
| • | The ALC relay control circuit is open for 5 seconds. |
| • | The ALC relay control circuit is shorted to ground for 5 seconds. |
Action Taken When the DTC Sets
| • | The SERVICE indicator will illuminate. |
| • | The check gauges chime sounds. |
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 ALC relay control circuit is open, the ALC headlamps will be inoperative. |
| • | In the ALC relay control circuit is shorted to ground, the ALC headlamps will be always on. |
| • | 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.
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Listen for an audible click when the ALC relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
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Tests for voltage at the coil side of the ALC relay. The LH HDLP fuse supplies battery positive voltage to the coil side of the ALC relay.
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Verifies that the body control module is providing ground to the ALC relay.
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Tests if ground is constantly being applied to the ALC relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics | |||
1 | Did you perform the Lighting System Diagnostic System Check? | Go to Step 2 | |
Does the ALC relay turn ON and OFF with each command? | 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 10 | |
Does the test lamp turn ON and OFF with each command? | Go to Step 8 | Go to Step 5 | |
Does the test lamp remain illuminated with each command? | Go to Step 7 | Go to Step 6 | |
6 | Test the control circuit of the ALC relay for 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 13 | Go to Step 9 |
7 | Test the control circuit of the ALC relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
8 | Inspect for poor connections at the ALC relay. 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 13 | Go to Step 11 |
9 | Inspect for poor connections at the harness connector of the body control module. 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 13 | Go to Step 12 |
10 | Repair the coil side battery positive voltage circuit of the ALC relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 13 | -- |
11 | Replace the ALC relay. Did you complete the replacement? | Go to Step 13 | -- |
12 |
Important: Perform the set up procedure for the body control module. Replace the body control module. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
