B2575 (W/TT6)
DTC B2575 (w/TT6)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC B2575 00
- Headlamp Control Circuit
Diagnostic Fault Information
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 low beam headlamp relay control circuit is open or shorted to voltage.
* When the BCM is not receiving a low beam headlamp request the low beam headlamp 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 (Headlights/Daytime Running Lights (DRL) Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the Low Beam Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
5. Disconnect the harness connector at the inoperative low beam headlamp.
6. Test for less than 5.0 ohms between B+ and the ground circuit terminal B.
• If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect a 20A fused jumper wire between the B+ circuit terminal 30 and the low beam headlamp control circuit terminal 87. Verify the low beam headlamps are ON.
• 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.
8. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
9. 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 the test lamp is always OFF, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always ON, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
10. If all circuits test normal, test or replace the Low Beam Relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Underhood Electrical Center or Junction Block Replacement (Underhood Electrical Center or Junction Block Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, programming, and setup