Operation

OPERATION

The Electric Vacuum Pump (EVP) system is installed to provide supplemental vacuum to the brake booster when the engine vacuum supply is low. The vacuum pump is connected to the engine and the brake booster through a series of hoses and one-way flow check valves. A pressure senor, mounted in the brake booster, provides information to the Antilock Brake System (ABS) module, then the vacuum level is sent over CAN to the Powertrain Control Module (PCM). The PCM modulates the EVP operation to maintain the brake booster vacuum within a given range. This system ensures that the customer experiences a consistent brake pedal feel under all driving conditions.

A two wire electrical connector is used to supply power and ground for the vacuum pump. Operating voltage is between 9V - 16V. Control of the vacuum pump is provided by the Powertrain Control Module (PCM) using a low side driver to a normally open relay (coil side). The relay coil side power is from a fuse in the under hood PDC. The switched power to the vacuum pump relay comes directly from the battery through an inline fuse holder located in the engine compartment.

The PCM monitors the Manifold Absolute Pressure (MAP) sensor and when the signal indicates low engine vacuum the PCM will cycle the vacuum pump as necessary to add vacuum to the power brake booster. The vacuum hoses are connected between the vacuum pump, the engine manifold (for MAP sensor signal), and the power brake booster vacuum sensor (on the brake booster). When the PCM cycles the vacuum pump on, the PCM monitors the MAP sensor and if the vacuum signal does not indicate a rising vacuum then DTCs will be set. Additionally the Antilock Brake System (ABS) module monitors the vacuum at the brake booster vacuum sensor and DTCs will also set in the ABS module.