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2016 – MX-5 – Brakes

ELECTRIC VACUUM PUMP CONTROL UNIT

Purpose

• The electric vacuum pump control unit calculates the input signals from the PCM, DSC HU/CM, vacuum sensor 1 and vacuum sensor 2, then it outputs a control signal to the electric vacuum pump and controls the electric vacuum pump drive and stoppage. The electric vacuum pump control unit also outputs the vacuum pressure conditions in the power brake unit to the DSC HU/CM.

Construction

System wiring diagram

Functions

Part name	Functions
Electric vacuum pump control unit	The electric vacuum pump control unit calculates the input signals from each module and sensor, and controls the electric vacuum pump drive and stoppage. Transmits the pressure (vacuum) in the power brake unit via CAN communication to the DSC HU/CM.
DSC HU/CM	Transmits brake fluid pressure, vehicle speed (estimated value) and DSC system condition via CAN communication to the electric vacuum pump control unit.
PCM	Transmits engine speed and vacuum sensor 2 detection value via CAN communication to the electric vacuum pump control unit.
Vacuum sensor 1	Transmits the vacuum value in the power brake unit to the electric vacuum pump control unit.
Vacuum sensor 2	Transmits the vacuum value in the power brake unit to the PCM.
Electric vacuum pump	Produces vacuum based on the electric vacuum pump control unit control signal and supplies it to the power brake unit.

Normal control

• The electric vacuum pump control unit compares the barometric pressure with the power brake unit vacuum when the ignition is switched ON and while the vehicle is being driven. If the difference is lower than the specified value, the electric vacuum pump control unit operates the electric vacuum pump.

• Under normal control, the value that is easiest for driving (High pressure = low vacuum) the electric vacuum pump among (select high type) the detected values in vacuum sensors 1 and 2 is used.

NOTE:

• After the ignition is switched from ON to OFF, the electric vacuum pump may operate if it is within the pre-determined time.

Fail-safe control

• If there is a malfunction in each signal necessary for control, the electric vacuum pump control unit performs the following controls indicated in the table.

• The electric vacuum pump warning light turns on to notify the driver that a malfunction has occurred in the system.(See BRAKE WARNING LIGHT/ABS WARNING LIGHT/ELECTRIC VACUUM PUMP WARNING LIGHT.)

Input signal	Control
Vehicle speed	Vehicle speed is regarded as specified value and performs normal control
Engine speed	Regarded as engine running and performs normal control
Brake fluid pressure	Performs normal control
DSC condition	Performs normal control
Vacuum sensor 1	Performs normal control using vacuum sensor 2
Vacuum sensor 2	Performs normal control using vacuum sensor 1

• If a malfunction occurs in which the power brake unit vacuum in the brake system may fail, the electric vacuum pump warning light and brake warning light turn on. (See BRAKE WARNING LIGHT/ABS WARNING LIGHT/ELECTRIC VACUUM PUMP WARNING LIGHT.)

• In this case, the electric vacuum pump is driven by the pre-determined pattern based on the brake pedal operation.

• If there is a malfunction in the electric vacuum pump system and the power brake unit vacuum fails, the DSC HU/CM performs a vacuum support function and inhibits the electric vacuum pump operation. (See DSC HU/CM.)

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