2010 Cadillac Truck SRX AWD V6-3.0L Page 298
Conditions for Running the DTC
The headlamps are turned ON.
Conditions for Setting the DTC
B257C 00
The headlamp control module detects a fault in the left low beam control circuit or an open/high resistance is the left low beam ground circuit.
B257D 00
The headlamp control module detects a fault in the right low beam control circuit or an open/high resistance is the right low beam ground circuit.
Action Taken When the DTC Sets
The appropriate headlamp is inoperative.
Conditions for Clearing the DTC
* The DTC will be current for as long as the fault is present.
* When the fault is no longer present, the DTC will be a history DTC.
* A history DTC will clear after 50 ignition cycles.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics (See: Diagrams/Electrical Diagrams/Lighting and Horns/System
Diagram/Headlights/Daytime Running Lights (DRL) Schematics)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views/Connector End Views By Name)
Description and Operation
Exterior Lighting Systems Description and Operation (See: Lighting and Horns/Description and Operation/Exterior Lighting Systems)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
Ignition ON, observe the function of the low beam headlamps while commanding the Low Beam Lamps ON and OFF with a scan tool. The E4G
headlamp-left low beam and the E4H headlamp-right low beam should turn ON and OFF while changing between the commanded states.
If the E4G headlamp-left low beam is always OFF, refer to Left Low Beam Inoperative
If the E4H headlamp-right low beam is always OFF, refer to Right Low Beam Inoperative
If both low beam headlamps are always ON or always OFF, refer to Headlamps Malfunction
Circuit/System Testing
Left Low Beam Inoperative
1. Ignition OFF, disconnect the X118 inline harness connector at the E4G headlamp-left low beam.
2. Connect a test lamp between the control circuit terminal G and ground.
3. Ignition ON, command the Low Beam Lamps ON with a scan tool, the test should illuminate while commanding the headlamp ON.
瀚慖f the test lamp does not illuminate and the circuit fuse is good, test the control circuit for an open/high resistance.
