A 2004 Bora 1.8L comfortable sedan, the owner of the car found in the car came abnormal sound. Repair workers found auxiliary brake vacuum pump long-term non-stop action, and occasionally will stop a few minutes.
    The engine control unit calculates the pressure of the brake booster according to the engine load, the speed, the throttle position and the brake light switch signal, and then carries on the pressure model of the intake manifold in the engine control unit Contrast, decide whether to open the vacuum pump. The car may be abnormal sound control tank is a link with a fault.
    Connect VAS5051, enter the 01 address, read the fault code with 02 function, showing three can not clear the permanent fault code, respectively, for the tank ventilation valve N80 failure, air flow meter G70 fault and oxygen sensor heater failure.
    Visual inspection found that the car to install their own anti-theft and reversing radar, and anti-theft speaker was a long self-tapping screws fixed on the firewall, too long screws into the engine electronic control unit of the main beam bundle, and make One of the lines break the ground. See the circuit diagram that this line is the air flow meter, fuel tank ventilation valve and oxygen sensor heating coil power supply, 3 lines share a fuse S243, the inspection fuse has blown fuse fuse caused by failure
    After the fuse blows, resulting in air flow meter, fuel tank ventilation valve, oxygen sensor heating coil without working power. If the engine electronic control unit does not receive the load signal (air flow meter signal), and in comparison with the standard data, will think that the brake vacuum pressure is insufficient, then control the auxiliary brake vacuum pump work, resulting in the failure.
    Re-bandage finishing line, then start the test, the fault code can be cleared, and no longer reproduce, auxiliary brake vacuum pump is no longer frequent action, the fault completely ruled out.
    In the troubleshooting, the idea must be open, especially a few fault code at the same time, and can not be cleared, usually between them have a certain connection, so use the method of associative thinking to analyze.