【Fault description】
    The engine can not start, self-diagnosis also failed.
    【Inspection process】
    Check the self-diagnosis system, prepare the number of engine check lights, the number of lights off. 1,2,3 forward number, waiting for the engine to check the light, but the left and so right, the engine check light is always off, and the charging light is not bright. Had to return to the starting point, asked the previous operation of the engine state, had had two times before the start of the situation, as the engine check light is not bright, there is no attention. First check the ignition spark, but no use, no sparks are not. There is no power supply for the primary terminal of the ignition coil. A look at the EFI (electronically controlled fuel injection) system, the main relay has been moving. Listen to the action of the nozzle sound, the nozzle did not move. Consider that there may be a problem with the engine control unit power supply, so start checking the fuse. Engine interior fuse box AM1, AM2, EFI 15A fuse is good, the car inside the right side of the 15A fuse is no problem.
    【Fault Analysis】
    The actual investigation, it is very complicated. First sort out the fault content as follows:
    ① engine check lights and charging lights in the ignition switch ON conditions are not bright;
    ② nozzle does not move;
    ③ ignition coil without power.
    From the convenience of the maintenance of the starting position, in any case have to restore self-diagnostic function. The reason the lamp does not light may also be broken filament, but the two bulbs at the same time the probability of filament is very small, so first from the power system to check.
    The wiring that is directly related to this fault is AM2-30A → Ignition switch AM2 → Ignition switch IG2 → Ignition fuse 15A. Investigate the ignition system of the ignition system, the result is the same as expected 0V, nozzle buck resistance is OV. Followed by the investigation of the car interior 15A fuse voltage, here is 0V. Once again returned to the engine room, measuring the output of the fusible connection AMz in the relay box, the result is 12V, good.
    At this point it can be concluded that the transmission of the engine compartment from the relay box to the car and the fuse inside the section of this line is very suspicious. And this section of the line is very difficult to check, as soon as possible to find the fault, but also access to this section of the wiring diagram. The detailed wiring diagram from the relay box to the 15A ignition fuse is shown in Figure 2.
    【Maintenance】
    Again from the easier place to start the investigation, lift the power steering system cover, check the ignition switch on the input side of the connector. AM1 of course is 12V, no problem. AM2 is 0V, that is, the power supply has not been sent to the input of the ignition switch to check the car interior relay station connector is particularly troublesome, leaving the final check, first check the engine room on the right side of the relay box inside the connector. The actual inspection, the connector on the input side is good, but the output side without power. Detailed inspection of the connector, the pins have been bent, and not inserted in the end, wiring is not good. Handle the wiring and trim the pins. The reason for no electricity is the poor contact of the connector.
   After finishing the wiring, the engine check lights, charging lights, etc. on the bright. Try to start the engine, the engine can start, but can not keep idling, and soon turn off. It is estimated that the self - diagnosis system has been restored and the investigation is carried out immediately. The result of the fault code is 31, and the fault code is "The engine speed is above 200r / min and the air flow meter does not output the KS signal for 2s.
    This engine air flow meter is the Carmen circulation flow meter, its structure shown in Figure 3; its circuit shown in Figure 4.