【Fault description】
    A BMW car, the engine idling instability, great jitter, oil smell heavier, when there are black smoke. The driver reflects the recent increase in fuel consumption, and the car dashboard "CHECKENGINE" warning lights do not go out.
    【Inspection process】
    The warning lamp does not go out, indicating that the engine is faulty. The use of the car's self-diagnosis fault function call out the fault code, that is, the ignition switch to the ignition file (not starting) after about 3s, the alarm light that regularly flash twice, and then repeat, that the fault code is "2" The Check the instructions, the fault location in the oxygen sensor signal, fuel injectors and idle control motor.
    An oxygen sensor mounted on the front of the exhaust pipe muffler is actually a solid battery. In normal work, can issue 0.25-0.85V electromotive force, corresponding to the thick and dense mixture of combustion conditions. The electromotive force feedback input to the computer (ECU) 28 feet and 10 feet to control the gasoline jet, to achieve the best air-fuel ratio (14.7). In order to shorten the heating process of the oxygen sensor, the sensor is electrically heated. Refer to Figure 2 (for the measurement, use a high impedance digital multimeter) for vehicle inspection. Detection found that the electromotive force is zero, indicating that the sensor has been damaged, so that the computer mistakenly received "thin" mixed gas signal, resulting in increased fuel consumption of the car, exhaust black smoke. To replace the new sensor, the engine back to normal operation, it was reduced to exclude.
    【Maintenance】
    After removing the fault, clear the fault code by rotating the ignition switch to "OFF" and disconnect the battery from the battery 15s (but be careful to prevent the loss of passwords such as "CD").