Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC 2575 00: Headlamp Control CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Headlamp Low Beam Relay Control | 2 | 1 | B2575 00 | -- |
| ||||
Circuit/System Description
Two different inputs to the body control module (BCM) can turn ON the low beam headlamps. The headlamp switch and the ambient light sensor.
Automatic Headlamps Operation
When the ambient light sensor detects a low light condition, the BCM then applies a ground to the headlamp low beam relay control circuit. This energizes the LO BEAM PCB relay and applies voltage through the LO BEAM fuses to the headlamp assemblies.
Headlamp Switch Operation
When the headlamp switch is placed in the ON position, ground is applied to the BCM through the headlamp switch headlamps ON signal circuit. The BCM then applies a ground to the headlamp low beam relay control circuit. This energizes the LO BEAM PCB relay and applies voltage through the headlamp LO BEAM fuses to the headlamps assemblies.
Conditions for Running the DTC
The ignition is ON. The headlamps must be commanded ON by the BCM from inputs by either the headlamp switch or the ambient light sensor.
Conditions for Setting the DTC
The BCM detects a short to voltage on the headlamp low beam relay control circuit while trying to energize the relay.
Action Taken When the DTC Sets
The BCM turns off the headlamp low beam relay control for the remainder of the ignition cycle.
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. |
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Ignition ON, turn the headlamps ON. The headlamps should illuminate.
Circuit/System Testing
- Ignition OFF, disconnect the C2 harness connector at the underhood fuse block.
- Connect a test lamp between the control circuit terminal 10 and B+.
- Command the Low Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the circuit tests normal, test or replace the underhood fuse block.
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
