Circuit Description
The body control module (BCM) grounds the headlamp relay control circuit when the ambient light sensor senses a dark condition. Voltage is supplied to the headlamp relay when the ignition is in the RUN position.
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 RUN position. |
| • | The ambient light sensor senses a dark condition. |
| • | The headlamp switch is in the AUTO position. |
| • | Transmission gear selectors not in the PARK position. |
Conditions for Setting the DTC
Any of the following conditions will set this DTC:
| • | The headlamp relay control circuit is open for 5 seconds. |
| • | The headlamp relay coil is open. |
| • | Ignition voltage to the headlamp relay is open. |
| • | The low beam signal circuit is open between the headlamp switch and the instrument panel (I/P) fuse block. |
| • | The headlamp relay output circuit is open. |
| • | The ground is open to the headlamp relay or switch. |
Action Taken When the DTC Sets
The headlamps will not illuminate in the AUTO position.
Conditions for Clearing the DTC
| • | The BCM receives the clear code command from the scan tool. |
| • | A current DTC will clear when the conditions for setting the DTC are no longer present. |
| • | A history DTC clears after 100 malfunction free ignition cycles. |
Diagnostic Aids
| • | Turn the ignition switch to the OFF position, cover the ambient light sensor on the instrument panel, wait for 15 seconds and then return the ignition to the ON position. The headlamps should illuminate. |
| • | If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | An open in the following circuits may cause DTC B2575: |
| • | Low beam signal circuit |
| • | Headlamp relay output circuit |
| • | Ground to the headlamp switch or relay |
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 headlamp 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 headlamp relay. The ignition switch supplies voltage to the coil side of the headlamp relay.
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Verifies that the BCM is providing ground to the headlamp relay.
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics | |||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 3 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||
2 |
Do the headlamps default to DRL and the DRL indicator illuminate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | ||||||
Does the headlamp relay turn ON and OFF with each command? | Go to Step 7 | Go to Step 4 | |||||||
Does the test lamp illuminate? | Go to Step 5 | Go to Step 11 | |||||||
Does the test lamp turn ON and OFF with each command? | Go to Step 9 | Go to Step 6 | |||||||
6 | Test the control circuit of the headlamp 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 15 | Go to Step 10 | ||||||
7 | Test the following circuits for high resistance or an open.
Did you find and correct the condition? | Go to Step 15 | Go to Step 8 | ||||||
8 | Inspect for poor connections at the headlamp switch. 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 15 | Go to Step 12 | ||||||
9 | Inspect for poor connections at the headlamp 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 15 | Go to Step 13 | ||||||
10 | 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 15 | Go to Step 14 | ||||||
11 | Repair the open in the coil side battery positive voltage circuit of the headlamp relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | -- | ||||||
12 | Replace the headlamp switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 15 | -- | ||||||
13 | Replace the headlamp relay. Refer to Relay Replacement in Wiring Systems. Did you complete the replacement? | Go to Step 15 | -- | ||||||
14 | 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 15 | -- | ||||||
15 |
Does the DTC reset? | Go to Step 3 | System OK | ||||||
