Circuit Description
The body control module (BCM) turns on the LOW BEAM relay when the ambient light sensor senses a dark condition or the low beam headlamps are requested ON. Battery positive voltage is supplied to the LOW BEAM relay at all times. The BCM grounds the LOW BEAM relay control circuit in order to activate the relay.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2575 Headlamp Control Circuit
Conditions for Running the DTC
| • | The ignition switch is in the ON position. |
| • | The ambient light sensor senses a dark condition, automatic lamp control (ALC) headlamps ON. |
Conditions for Setting the DTC
| • | B2575 01 will set if there is a short to voltage in the low beam relay control circuit. |
| • | B2575 06 will set if there is an open or short to ground in the low beam relay control circuit. |
Action Taken When the DTC Sets
| • | The SERVICE indicator illuminates. |
| • | The check gages 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
| • | Turn the ignition switch to the OFF position, cover the ambient light sensor on the dash, wait for 15 seconds, and then return the ignition to the ON position. The low beam headlamps should illuminate. |
| • | If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections . |
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 LOW BEAM relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
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This step tests for voltage at the coil side of the LOW BEAM relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Does the LOW BEAM relay turn ON and OFF with each command? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | |
3 | Is DTC B2575.01 set? | Go to Step 6 | Go to Step 4 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 10 | |
5 |
Does the test lamp turn ON and OFF with each command? | Go to Step 8 | Go to Step 7 |
6 | Test the control circuit of the LOW BEAM relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
7 | Test the control circuit of the LOW BEAM relay for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
8 | Inspect for poor connections at the LOW BEAM relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . 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 (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
10 | Repair the open in the coil side battery positive voltage circuit of the LOW BEAM relay. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 13 | -- |
11 | Replace the LOW BEAM relay. Refer to Relay Replacement . Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the BCM. Refer to Control Module References for BCM replacement, setup, and programming. Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
