Buick Regal: DTC C025E

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.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

DTC Descriptor

DTC C025E

Brake Booster Vacuum Sensor Circuit

For symptom byte information refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

The brake booster vacuum sensor monitors the pressure in the brake booster. The electronic brake control module supplies a 5 V reference and a low reference circuit to the brake booster vacuum sensor. The vacuum sensor supplies a voltage signal in relation to the pressure in the brake booster to the electronic brake control module.

Conditions for Running the DTC

C025E 00, C025E 01, C025E 06, C025E 1F

Ignition ON

C025E 5A

• Ignition ON.
• Brakes are not applied.

Conditions for Setting the DTC

C025E 00

• A short to ground is detected on the 5V reference circuit.
• A short to voltage is detected on the 5V reference circuit.

C025E 01

• A short to voltage is detected on the signal circuit.
• An open/high resistance is detected on the low reference circuit.

C025E 06

• An open/high is detected on the signal circuit.
• A short to ground is detected on the signal circuit.
• An open/high is detected on the 5V reference circuit.

C025E 1F

The vacuum sensor signal is erratic.

C025E 5A

The vacuum sensor signal is not plausible.

Action Taken When the DTC Sets

Service Brake Assist message is displayed on the driver information center

Conditions for Clearing the DTC

The DTC clears when the diagnostic runs and passes

Reference Information

Schematic Reference

Hydraulic Brake Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Brake Assist System Description and Operation

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Refer to Control Module References for scan tool information

Circuit/System Verification

1. Verify that the brake booster vacuum system has no damage, leakage or incorrect installation.

• If damage, leakage or incorrect installation is found

Refer to Brake Assist System Diagnosis

• Go to next step: If no damage, leakage or incorrect installation is found

2. Refer to Circuit/System Testing.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B19B Brake Booster Vacuum Sensor. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the low reference circuit terminal 2 and ground.

• If 10 Ω or greater

1. Disconnect the harness connector at the K17 Electronic Brake Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K17 Electronic Brake Control Module.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 3 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K17 Electronic Brake Control Module.

If greater than 5.2 V

1. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K17 Electronic Brake Control Module.

• Go to next step: If between 4.8 - 5.2 V

5. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module, Ignition ON.

6. Test for less than 1 V between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and ground.

• If greater than 1 V

Repair the short to voltage on the circuit.

• Go to next step: If less than 1 V

7. Ignition OFF.

8. Test for infinite resistance between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and ground.

• If less than infinite resistance

Repair the short to ground on the circuit.

• Go to next step: If infinite resistance

9. Test for less than 2 Ω between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and the K17 Electronic Brake Control Module signal circuit terminal 34.

• If 2 Ω or greater

Repair the open/high resistance in the circuit.

• Go to next step: If less than 2 Ω

10. Test or replace the B19B Brake Booster Vacuum Sensor.

11. Verify the DTC does not set while operating the vehicle under Conditions for Running the DTC.

• If the DTC sets

Replace the K17 Electronic Brake Control Module.

• Go to next step: If the DTC does not set

12. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Refer to Power Brake Booster Vacuum Sensor Replacement (2.0L LTG) or Power Brake Booster Vacuum Sensor Replacement (3.6L LGX)
• Refer to Control Module References for electronic brake control module replacement, programming and setup

READ NEXT: