2010 Cadillac CTS Sedan AWD V6-3.6L Page 636
the BCM will apply battery voltage to the right and left stop lamp control circuits, transmission control module (TCM), engine control module
(ECM), and center high mounted stop lamp (CHMSL) control circuit.
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The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an
analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5 V
reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied,
the BCM will apply battery voltage to stop lamp relay coil side control circuit, transmission control module (TCM), engine control module (ECM),
and center high mounted stop lamp (CHMSL). When the stop lamp relay receives battery voltage from the BCM, the relay coil is energized and the
stop lamp relay switch contacts close applying battery voltage from the STOP LAMPS fuse to illuminate the rear stop lamps and trailer stop lamps.
Conditions for Running the DTC
* Battery voltage must be between 9-16 V.
* Brakes APPLIED.
Conditions for Setting the DTC
DTC B3445 00
The BCM detects a short to ground in the CHMSL control circuit when the stop lamps are being commanded ON.
DTC B3884 00
The BCM detects a short to ground in the CHMSL control circuit when the stop lamps are being commanded ON.
Actions Taken When the DTC Sets
The BCM will not illuminate the CHMSL.
Conditions for Clearing the DTC
* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 malfunction-free ignition cycles have occurred.
Diagnostic Aids
Note: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation,
refer to Exterior Lighting Systems Description and Operation (See: Lighting and Horns/Description and Operation/Exterior Lighting Systems
Description and Operation).
Reference Information
Schematic Reference
Exterior Lights Schematics (See: Diagrams/Electrical Diagrams/Lighting and Horns/System Diagram/Exterior Lights Schematics)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (See: Lighting and Horns/Description and Operation/Exterior Lighting Systems Description
and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit
Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Wiring Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Ignition OFF, test for less than 5.0 ohm between the ground circuit terminal B and ground.
