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 B2575 00: Headlamp Control CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
HDM Relay Fuse B+ | 1 | 1 | -- | -- |
HI HEADLAMP relay B+ | 2 | 2 | -- | -- |
IGN COILS Relay Fuse B+ | 2 | 2 | -- | -- |
DRL Defeat Switch Signal | 3 | 3 | 3 | -- |
Headlamp High Beam Switch Signal | 4 | 4 | 4 | -- |
Headlamp Flash to Pass Switch Signal | 4 | 4 | 4 | -- |
Headlamp ON Switch Signal | 3 | 3 | 3 | -- |
Low Beam Headlamp Relay Control | B2575 00 | B2575 00 | B2575 00 | -- |
Headlamp ON Indicator Control | B3802 00 | 3 | 3 | -- |
High Beam Headlamp Relay Control | B2580 00 | B2580 00 | B2580 00 | -- |
Low Beam Headlamp Control | 1 | 1 | 1 | -- |
High Beam Headlamp Control | 2 | 2 | 2 | -- |
Headlamp ON Indicator Low Reference | 3 | 3 | 3 | -- |
HDM Relay Ground | -- | 1 | -- | -- |
Headlamp Switch Ground | -- | 3 | -- | -- |
Turn Signal/Multifunction Switch Ground | -- | 4 | -- | -- |
Left Headlamp Ground | -- | 1 | -- | -- |
Right Headlamp Ground | -- | 1 | -- | -- |
1. Headlamp Malfuntion - Low Beam 2. Headlamp Malfuntion - High Beam 3. Headlamp Switch Malfunction 4. Turn Signal/Multifunction Switch Malfunction | ||||
Circuit/System Description
The HDM and high beam relay receive battery voltage directly from the battery. The BCM supplies a 100% duty cycle PWM ground signal to the HDM for automatic low beam headlamp control and normal low beam headlamp operation. The BCM also supplies ground to the high beam relay coil for high beam headlamp operation. When the driver places the headlamp switch in the HEADLAMP position and the dimmer switch is in the low beam position, the HDM switches to full output sending current flow through the left and right low beam headlamp fuses to both low beam headlamps. The dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-Pass (FTP) position from G102 to deactivate the low beam headlamps and activate the high beam headlamps. With the headlamps in the low beam position, the high beams may be momentarily turned on or flashed by activating the FTP portion of the switch.
Conditions for Running the DTC
The battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
| • | When the BCM receives a low beam headlamp request the HDM relay control circuit is open or shorted to voltage. |
| • | When the BCM is not receiving a low beam headlamp request the HDM relay control circuit is shorted to ground. |
Action Taken When the DTC Sets
The low beam headlamps will be inoperative or always on.
Conditions for Clearing the DTC
| • | This DTC will clear on current status after the condition for setting the fault is corrected. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the HDM relay.
- Verify that a test lamp illuminates between B+ and the ground circuit terminal 6.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 4 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal 2 and ground.
- Disconnect the harness connector at the inoperative low beam headlamp.
- Test for less than 5.0 ohms between B+ and the ground circuit terminal B.
- Connect a 15A fused jumper wire between the B+ circuit terminal 2 and the low beam headlamp control circuit terminal 4. Verify the low beam headlamps are ON.
- Connect a test lamp between the ground circuit terminal 6 and the control circuit terminal 5.
- Command the low beam headlamps ON and OFF with the headlamp switch. The test lamp should turn ON and OFF between the commanded states..
- If all circuits test normal, test or replace the HDM relay.
| ⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, and the B+ circuit fuse is open, test the control circuit terminal 4 for a short to ground. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the headlamps are always OFF, test the control circuit for a short to ground or an open high resistance. |
| ⇒ | If the headlamps are always ON, test the control circuit for short to voltage. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. 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, programming, and setup.
