GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 LaCrosse 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B3445

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 B3445: Stop Lamp Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Stop Lamp Switch Signal

B3445, P0573

P0573

P0572

--

Circuit/System Description

When the brake pedal is applied, the BCM receives a brake applied signal from the brake pedal position sensor (BPPS). The BCM applies B+ to the stop lamp switch signal circuit. This circuit supplies a B+ signal to the powertrain control module (PCM) (L26), engine control module (ECM) (LY7), transmission control module (TCM) (LY7), throttle actuator control (TAC) module, and electronic brake control module (EBCM) indicating the brakes are applied. B+ is also supplied to the center high mound stop lamp (CHMSL), illuminating it when the brakes are depressed.

Conditions for Running the DTC
    • The ignition is ON
    • The stop lamps are commanded ON

Conditions for Setting the DTC

The BCM detects a short to ground on the stop lamp switch signal circuit when the stop lamps are being commanded ON.

Action Taken When the DTC Sets

Output on the stop lamp switch signal circuit is disabled.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists
    • A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Testing

RPO L26

  1. Ignition OFF, disconnect the harness connector at the CHMSL.
  2. Test for less than 5 ohms of resistance between the ground circuit terminal B and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the signal circuit terminal A and ground.
  4. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
    5. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. Ignition OFF, connect the harness connector at the CHMSL. Disconnect the harness connector at the TAC module.
  6. Connect a test lamp between the signal circuit terminal 6 and ground.
  7. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
    8. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. Ignition OFF, connect the harness connector at the TAC module. Disconnect the harness connector at the EBCM.
  9. Connect a test lamp between the signal circuit terminal 6 and ground.
  10. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
    11. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance.
  11. Ignition OFF, connect the harness connector at the EBCM. Disconnect the X1 harness connector at the PCM.
  12. Connect a test lamp between the signal circuit terminal 32 and ground.
  13. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
    14. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance.

RPO LY7

  1. Ignition OFF, disconnect the harness connector at the CHMSL.
  2. Test for less than 5 ohms of resistance between the ground circuit terminal B and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the signal circuit terminal A and ground.
  4. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
    5. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. Ignition OFF, connect the harness connector at the CHMSL. Disconnect the harness connector at the TCM.
  6. Connect a test lamp between the signal circuit terminal 42 and ground.
  7. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
    8. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. Ignition OFF, connect the harness connector at the TCM. Disconnect the harness connector at the EBCM.
  9. Connect a test lamp between the signal circuit terminal 6 and ground.
  10. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
    11. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance.
  11. Ignition OFF, connect the harness connector at the EBCM. Disconnect the X2 harness connector at the ECM.
  12. Connect a test lamp between the signal circuit terminal 10 and ground.
  13. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
    14. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup, and programming