Pass multiple test runs. Finding the above-mentioned appearance of the fault: Only when the car is continuously driving, the automatic transmission will lock the gear and enter the protection mode. At this time, if the engine is turned off for a few seconds and the car is driven again, the automatic transmission will return to normal operation. According to the analysis of the failure law, the temperature of the engine and the automatic transmission changes with the travel time, which is likely to be a stable display of a control or a working element of the automatic transmission. Check intake manifold, no leakage; check throttle control mechanism, no problem; check idle motor, normal. Then read the engine dynamic data flow, and found that there are four items of data is not normal, these four data are: injection pulse width is 7.30ms at idle (normal value is 2.6ms), the signal pressure of the intake manifold absolute pressure sensor is 3.3V (normal value should be 1.sv), the idle motor step number is 102 (normal value is 30), ignition advance angle is l to 20, and unstable. Comprehensive analysis of the above four items of data, the focus of conflict is concentrated on the intake manifold absolute pressure sensor, its signal voltage is too high, making the injection pulse width increases. At this point, the oxygen sensor detected a rich mixture. The engine electronic control unit then instructs the idling stepper motor to increase the intake air volume, thereby causing an increase in the number of idling steps, and the engine electronic control unit also continuously adjusts the mixture to check that the intake manifold is not leaking. Further inspections found that the engine is powerful and has good power. This means that there will be no problem with mismatched valve timing and blocked exhaust pipes. Vacuum is applied to the intake manifold absolute pressure sensor by the vacuum gun. The sensor indicates that the sensor is normal. Based on the above inspection results, it is concluded that the fault location may be in the EGR system. After dismantling inspection, it was found that the EGR solenoid valve was stuck in the open position, the exhaust back pressure tube was broken, and the exhaust back pressure valve base was severely cracked. Replace EGR solenoid valve troubleshooting. According to past experience, the first thought was the automatic transmission control unit, and some of its electronic components were suspected to have become abnormal at high temperatures. Then they put on a normal running vehicle with the same type of automatic transmission control unit, and the failure still failed. exclude.
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