News

A 2010 wheel Reno Coro four wheel drive SUV with a mileage of about 95 thousand km. Users reflect: the engine fault lights and ESP fault lights are abnormal and the engine can not be accelerated. After the car: first test the car to verify the fault. It is found that the engine fault lights and ESP fault lights are always bright, and no matter how to step on the accelerator pedal, the engine speed is always about 1700 r/min, and the engine ECU enters the failure mode. Connect the CLIP to read the fault code. The fault code stored in the engine ECU is DF078, which means the electronic throttle control circuit fault; the fault code stored in ABS is DF034, meaning the engine ECU to ESP connection fault. According to the above test results, the causes may be as follows: ESP fault, electronic throttle failure, engine ECU fault, acceleration pedal position sensor fault, related line and connector fault. According to the maintenance experience of similar fault car, first check the wire harness connector of ESP, electronic throttle and engine ECU. After the connector is processed and inserted firmly, the CLIP is connected, the ignition switch is connected, the fault code is cleared and the fault code can be cleared. But after starting the engine for a period of time, the trouble code appears again. Therefore, it is possible to basically eliminate the possibility of poor contact between connectors and failure of lines. According to the fault phenomenon, the above fault code is analyzed, and DF078 is considered as the main fault, and DF034 is only a derived fault, because if there is a connection fault between the engine ECU and the ESP, then CLIP should be able to detect the fault after the ignition switch is switched on, not the failure after the starting of the engine. So the focus of the investigation is on the electronic throttle control system. The electronic throttle is driven by a DC motor. The engine ECU controls the throttle valve to turn on or off by changing the polarity of the power supply. The engine ECU first determines the accelerator pedal position according to the signal of the acceleration pedal position sensor, and then controls the throttle opening or closing according to the driver's needs; the throttle position sensor feedback the actual throttle opening to the engine ECU, and then the engine ECU corrects the value. To view the engine data flow, as the accelerator pedal is stepped on, the acceleration pedal position sensor signal voltage increases and the signal voltage of the accelerator pedal is loosened gradually, indicating that the accelerator pedal position sensor is normal, but in the starting state, no matter what position is accelerated, the signal power of the throttle position sensor is in the starting state. The pressure is basically unchanged. That is to say, the engine ECU can not control the throttle to achieve the corresponding opening after receiving the accelerator pedal position signal. The suspicion is that there is a problem between the throttle DC motor and the ECU, resulting in ECU unable to control the throttle operation. However, there is no short circuit or open circuit fault between the throttle DC motor and the engine ECU, which indicates that there is a fault in the electronic throttle. Troubleshooting: replace the electronic throttle assembly, execute the initialization procedure and remove the fault code.