Buick Regal: Brake Booster Vacuum Assist Description and Operation

System Component Description

B19B - B19B Brake Booster Vacuum Sensor
K17 - K17 Electronic Brake Control Module
M9 - M9 Brake Booster Pump Motor

The brake booster vacuum assist system consists of the following:

Brake Booster Auxiliary Vacuum Pump (electric or mechanical)

The brake booster vacuum pump is a secondary vacuum supply to the brake booster used to maintain sufficient vacuum for brake assist.

Brake Booster Vacuum Sensor

The vacuum sensor is used to measure the level of vacuum available 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 is located in the brake booster or vacuum hose. The brake booster vacuum sensor supplies a voltage signal in relation to the pressure in the brake booster to the electronic brake control module.

Electronic Brake Control Module

The electronic brake control module monitors the vacuum in the brake booster using the brake booster vacuum sensor. When the vacuum within the system drops the electronic brake control module turns ON the brake booster auxiliary vacuum pump.

Vacuum Brake Booster

When brake system input force is applied, air at atmospheric pressure is admitted to the rear of both vacuum diaphragms, providing a decrease in brake pedal effort required. When input force is removed, vacuum replaces the atmospheric pressure within the booster. The booster uses source vacuum to decrease the effort required by driver when applying the brake.

Vacuum Source

Vacuum is supplied by the engine vacuum or by the brake booster auxiliary vacuum pump (electric or mechanical).

System Operation

The electric pump can be switched on and off by the electronic brake control module based on the required vacuum. Pressure variations during braking can be measured, and the pump can be activated to generate additional vacuum if required to increase the braking force.

BRAKE FLUID AND BRAKE FLUID HANDLING

WARNING: Brake fluid may irritate eyes and skin. In case of contact, take the following actions:

• Eye contact - rinse thoroughly with water.
• Skin contact - wash with soap and water.
• If ingested - consult a physician immediately.

CAUTION: When adding fluid to the brake fluid reservoir or to the clutch fluid reservoir, use only DOT-4+ brake fluid from a clean, sealed container. This polyglycol brake fluid is hygroscopic and absorbs moisture. Do not use fluid from an open container that may be contaminated with water. Improper or contaminated fluid could result in damage to the system components. CAUTION: Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills. CAUTION: Avoid spilling brake fluid on any of the vehicle's painted surfaces, wiring, cables or electrical connectors. Brake fluid will damage paint and electrical connections. If any fluid is spilled on the vehicle, immediately flush the area with water to minimize the potential for damage. CAUTION: Power steering fluid, engine oil, brake fluid, or any mineral based fluids cannot be mixed. If brake seals contact power steering fluid or steering seals contact brake fluid, seal damage will result.

NOTE:

• Do not reuse the brake fluid collected during the hydraulic brake system bleeding.
• Always store brake fluid in a closed container.
• Reseal brake fluid containers immediately after use.
• Do not use brake fluid left in an open container.
• Do not use brake fluid left in an improperly sealed container.
• Do not use the following fluids in the hydraulic brake system:
  • Power steering fluid
  • Automatic transmission fluid
  • DOT 5 silicone hydraulic brake fluid

BRAKE WARNING SYSTEM DESCRIPTION AND OPERATION

Brake Warning Indicator

P16 - P16 Instrument Cluster
B20 - B20 Brake Fluid Level Switch
K17 - K17 Electronic Brake Control Module

The instrument cluster turns the brake warning indicator ON when the following occurs:

• The instrument cluster performs the bulb check. The brake warning indicator illuminates for 5 s.
• When the electronic brake control module (EBCM) detects low brake fluid level it sets DTC C0267 and sends a serial data message to the instrument cluster, which will illuminate the red brake indicator.

Driver Information Center Messages

When the electronic brake control module (EBCM) detects low brake fluid level it sets DTC C0267 and sends a serial data message to the driver information center, which will display Brake Fluid Low message.

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