Why Magotan sedan EPC meter lights up

Failure phenomenon: a 2009 models FAW – Volkswagen Magotan 1.8TSI car, say users, driving the car to accelerate bad, EPC warning lamp on the instrument lighting.

Check Analysis: VAS5051 fault diagnostic detection, the engine control unit stores the fault code 08852 (fuel pressure regulating valve N276 open circuit), the fault is a permanent fault code, can not be cleared. Group 3 data stream read 01-08-140 area, when displaying the idle fuel pressure is 700 kPa, the standard value should be about 4 MPa, the detection results indicate a high pressure fuel system can not be established.


FIG. 2

The mass PQ46 platform magotan cars equipped with a power controlled fuel injection engine, the high fuel pressure is adjusted (FIG. 1) mounted on the fuel pump by a pressure regulator N276. In the injection process, the engine control unit controls the start point based on the calculated fuel supply pressure valve to send instructions N276 pull it, this time against the force of needle spring forward movement of the needle valve, the spring force of the inlet valve under it is closed. With the upward movement of the pump piston, the hydraulic pressure in the pump chamber to establish, when the pump chamber is higher than the hydraulic oil pressure in the fuel rail, the oil valve is forcibly opened, the fuel will be pumped into the fuel rail. Forming a stable high pressure fuel in the fuel rail by the pressure sensor and the identification signal to the engine control unit, by reading the data stream 01-08-140 set pressure display area 3 we can analyze whether the high pressure set up. Based on the above analysis process of establishing high-pressure fuel, the likely cause of the high-pressure fuel supply system can not be established comprising: a camshaft driving device is damaged, a high pressure booster pump failure, high pressure booster pump electronic control unit and an engine control fault line fault. But the combination of fault codes pressure regulating tips valve N276 interruption, it is necessary first of all self-diagnostic function adjustment line valve N276 of the fuel pressure through the actuator VAS5051 tested, found for a touch shell N276 when performing self-diagnosis without any reaction, and not heard by the engine control unit by controlling the pull of a certain frequency ldquo; clicking rdquo; sound, this time VAS5051 self-diagnosis performed interface display system activation circuitClosed (FIG. 2). Thus the possibility of determining the initial presence of the engine control unit controls not a fault, the fault point to be locked in the execution of the line N276.

The control circuit diagram of a regulator N276 (FIG. 3), the regulator N276 total two terminals. T2gz / 1 terminal via the high pressure pump SB17 fuse link engine control relay J49 87 feet, for providing power supply from the main relay; T2gz / 2 terminal to the engine control unit T60ya / 19 terminal for receiving operational control of the control unit signal. Tip recombination fault code, analyzes possible reasons include: N276 internal circuit breaker; T60ya N276 circuit breaker between the T2gz / 2 terminal to the engine control unit / terminal 19; in the N276 T2gz / 1 terminals of the high pressure pump to the engine control relay circuit breaker 87 between the legs of the terminals J49; J49 relay circuit breaker itself; J49 peripheral power supply line circuit.

Figure 3

Figure 4

N276 disconnect the harness connector to T2gz / 1 is a measurement point, detecting the state of the ignition of the engine control waveform is a normal negative trigger waveform (FIG. 4), indicating that the wireless path between the N276 T2gz / 2 terminal to the engine control unit T60ya / 19 terminal circuit phenomenon. N276 to the T2gz / 1 terminal measurement point, detecting the non-feeding state in the ignition voltage, whereby the power supply circuit can be inferred when disconnection failure occurs N276. J49 measuring the high pressure pump control relay 87 to the terminal pin T2gz / 2 feet N276 normal line, thereby determining the cause of the fault or internal relay J49 peripheral power supply. J49 relay center to detect, measure the 30 normal supply voltage terminal, pin 85 by control from the main relay SB23, measured for a normal power source 15. J49 further measurement control relay coil resistance (85 feet and 86 feet) for the standard resistor 82 Omega ;, normal contrast, normal preliminary test element, but the power line shortage. In order to track this problem, open relay case, observed at the end of the ignition relay gear executed not pull 2 ​​contacts described relay control coil inside in operationVirtual connection does not provide a closed loop pull force required to perform.

Figure 5

Solution: Replace the relay J49 (FIG. 5), clear fault code 08852. In this case the test function VAS5051 reuse, N276 into the engine system performs self-diagnostic element can be heard ldquo N276 according to a certain frequency of pull; clicking rdquo; sound, indicating that the engine control unit to control a high pressure booster pump back to normal, At this time, the fuel pressure 140 working group is displayed when reading the idling 4 MPa, the failure so far to solve.

reviewed: Incidentally, for magotan car, the high-pressure fuel can not be established due to the high pressure regulator fault basically an internal mechanical failure of the pump, the pump piston is generally jamming bottom dead center , can not be effective stroke camshaft driven by the cylinder plunger, thereby failing to establish the required hydraulic pressure corresponding to the injection. The engine control unit monitors the oil pressure to the operating range of tolerance values, then no integrated electric disconnection fault code identifying the logical analysis of the high pressure booster pump, thus malfunction code 08851 (fuel pressure regulating valve N276 mechanical failure) fault code storage . And in this case is because the relevant control circuit breaker, resulting in a fault code memory 08852, and we can see the same phenomenon but the causes of failure are very different, which suggests that we in the maintenance of electrical control failure, must comply with a comprehensive analysis of the diagnostic testing process , targeted to solve the problem, in order to avoid misunderstanding empiricism.

(the valley towards the peak)

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