Buick Regal: Stop Lamps Malfunction
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.
Diagnostic Fault Information
1. Stop Lamps Malfunction
2. Center High Mounted Stop Lamp Malfunction
Circuit/System Description
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 the left and
right stop lamp control
circuits as well as the center high mounted stop lamp control circuit
illuminating the left and right stop
lamps and the center high mounted stop lamp.
Diagnostic Aids
When testing at the stop lamp bulb sockets, make sure all measurements and
test lamp connections are
in the correct terminal location and do not come in contact with each other
during testing.
Reference Information
Schematic Reference
Exterior Lights Wiring Schematics
Connector End View Reference
COMPONENT CONNECTOR END VIEWS - INDEX
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 Verification
1. Ignition ON.
2. Verify the scan tool Brake Pedal Applied parameter changes between Active and
Inactive while
pressing and releasing the brake pedal.
- If the parameter does not change
Refer to Circuit/System Testing - Brake Pedal Position Sensor
Malfunction.
- Go to next step: If the parameter changes
3. Verify the left brake lamp turns ON and OFF when commanding the Left Stop
Lamp ON and OFF
with a scan tool.
- If the left brake lamp does not turn ON and OFF
Refer to Circuit/System Testing - Stop Lamps Malfunction.
- Go to next step: If the left brake lamp turns ON and OFF
4. Verify the right brake lamp turns ON and OFF when commanding the Right
Stop Lamp ON and
OFF with a scan tool.
- If the right brake lamp does not turn ON and OFF
Refer to Circuit/System Testing - Stop Lamps Malfunction.
- Go to next step: If the right brake lamp turns ON and OFF
5. Verify the center high mounted stop lamp turns ON and OFF when commanding
the Center Stop
Lamp ON and OFF with a scan tool.
- If the center high mounted stop does not turn ON and OFF
Refer to Circuit/System Testing - Center High Mount Stop Lamp
Malfunction.
- Go to next step: If the center high mounted stop turns ON and OFF
6. All OK.
Circuit/System Testing
Brake Pedal Position Sensor Malfunction
1. Ignition OFF, disconnect the harness connector at the B22 Brake Pedal
Position Sensor, ignition
ON.
2. Test for less than 1 V between the low reference circuit terminal 1 and
ground.
- Ignition OFF, disconnect the X1 harness connector at the K9 Body Control
Module, ignition
ON.
- Test for less than 1 V between the low reference circuit and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K9 Body Control Module.
- Go to next step: If less than 1 V
3. Test or replace the B22 Brake Pedal Position Sensor.
Stop Lamps Malfunction
1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the
appropriate E4 Turn
Signal Lamp. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 15 Ω between the ground circuit terminal B and ground.
- Ignition OFF.
- Test for less than 2 Ω in the ground circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, repair the open/high resistance in the ground
connection.
- Go to next step: If less than 15 Ω
3. Connect a test lamp between the control circuit terminal A and ground,
ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the appropriate Stop
Lamp ON and
OFF with a scan tool.
- If the test lamp is always OFF
- Ignition OFF, disconnect the appropriate harness connector listed below
at the K9 Body
Control Module.
- X4 left stop lamp
- X5 right stop lamp
- Test for infinite resistance between the control circuit and ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- Go to next step: If infinite resistance
- Test for less than 2 Ω in the control circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, replace the K9 Body Control Module.
- If the test lamp is always ON
- Ignition OFF, disconnect the appropriate harness connector listed below
at the K9 Body
Control Module, ignition ON.
- X4 left stop lamp
- X5 right stop lamp
- Test for less than 1 V between the control circuit terminal and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K9 Body Control Module.
- Go to next step: If the test lamp turns ON and OFF
5. Test or replace the appropriate E4 Turn Signal Lamp.
Center High Mount Stop Lamp Malfunction
1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the
E6 Center High
Mounted Stop Lamp. It may take up to 2 min for all vehicle systems to power
down.
2. Test for less than 15 Ω between the ground circuit terminal 2 and ground.
- Ignition OFF.
- Test for less than 2 Ω in the ground circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, repair the open/high resistance in the ground
connection.
- Go to next step: If less than 15 Ω
3. Connect a test lamp between the control circuit terminal 1 and ground,
ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the Center Stop Lamp ON
and OFF
with a scan tool.
- If the test lamp is always OFF
- Ignition OFF, disconnect the X4 harness connector at the K9 Body Control
Module.
- Test for infinite resistance between the control circuit and ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- Go to next step: If infinite resistance
- Test for less than 2 Ω in the control circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, replace the K9 Body Control Module.
- If the test lamp is always ON
- Ignition OFF, disconnect the X4 harness connector at the K9 Body Control
Module, ignition
ON.
- Test for less than 1 V between the control circuit terminal and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K9 Body Control Module.
- Go to next step: If the test lamp turns ON and OFF
5. Test or replace the E6 Center High Mounted Stop Lamp.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- High Mount Stop Lamp Replacement (Wagon) High Mount Stop Lamp
Replacement
(Hatchback)
- Brake Pedal Position Sensor Replacement
- Brake Pedal Position Sensor Calibration
- Rear Body Structure Stop Lamp Replacement (5-Door Hatchback 68) Rear
Body Structure
Stop Lamp Replacement (5-Door Wagon 35)
- Control Module References for BCM replacement, programming, and setup
READ NEXT:
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.
Diag
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.
Diag
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