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Troubleshooting of EPC lamp alarm for Volkswagen
  • Automotive

A Volkswagen ten miles B7L 1.8 car with a mileage of about 15 thousand km in 2013. User response: the vehicle is running poorly, and the dashboard EPC light is on the alert. Fault diagnosis: using VAS5052A to detect engine control unit, store fault code "00135, fuel rail / system pressure is too low, static". Clear the fault code, accelerate the journey for a short distance, and reappear the trouble code. The possible reasons for this fault code: fuel pump controller, fuel pump power supply line, fuel pump and filter, low pressure fuel line, fuel pressure regulating valve N276 and line, engine control unit and other faults. Connect VAS5052A, the test car found that the idle speed, uniform speed or slow acceleration are normal, rapid acceleration engine jitter, EPC alarm, the maximum speed of less than 3000r/min. At this time, the oil pressure of the low pressure system (1 bar=105Pa) was read (1 bar=105Pa), and the oil pressure of the high pressure system (group 01-08-140 3) was read. The normal value was 50 to 150bar. In cylinder direct injection engine, the oil pressure of the high pressure system is regulated by the pressure regulating valve N276 on the fuel pump. In the fuel injection process, the engine control unit sends instructions to the fuel pressure control valve N276 according to the calculated oil supply starting point. As the plunger moves upward, the oil pressure is set up in the pump chamber. When the oil pressure in the pump is higher than the oil pressure in the oil rail, the oil discharge valve is forced to open, and the oil is pumped into the rail. The high voltage sensor sends the signal to the engine control unit and reads the oil pressure of the high pressure system through the data stream. In order to get normal data, the fuel pressure regulating valve N276 of a normal car is pulled out, the pressure of the high pressure system is about 7bar, and the pressure of high pressure is only 4bar when the car fails, and it is lower than the low pressure fuel pressure of 6bar, and it is doubted that the inlet of the high pressure pump is blocked. After the replacement of the high-pressure pump, the fault still remains. If the high-pressure pipeline is removed, the check valve is found to be floc when the one-way valve is removed. Maintenance summary: because the one-way valve has flocculent, but not completely blocked into the oil pipe, acceleration fuel flow speed, foreign body completely blocked high pressure pump inlet, thus engine acceleration bad, EPC lamp alarm.

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