Chevrolet lumina suddenly flameout
  • Automotive

A Chevrolet mileage 3.8L wagon with a mileage of about 130 thousand km and a V6 engine and automatic transmission. User response: when the vehicle suddenly stalled, it was dragged into the repair shop and diagnosed as no high pressure fire and fuel injection. Turn on the ignition switch and the engine fault light on the dashboard illuminate the power supply of the power system control module (PCM). The terminals A and B of the short diagnostic block read the fault codes, and the results are normal. The ignition system of the car is called the C3I system, and the ignition control module (I CM) should be checked first without the high pressure fire, without considering the PCM, because the high pressure fire is produced directly by the ICM. The ICM is equipped with 3 ignition coils. Its external circuit connects two sensors: the camshaft speed sensor and the crankshaft speed sensor. The camshaft speed sensor (3 pin) produces the 1x signal; the crankshaft position sensor (4 PIN) produces 3x and 18x signals. When the three signals of 1X, 3x and 18x input the ignition control module at the same time and the phase is correct, the ignition control module produces the ignition signal, and the 3 ignition coils are controlled to produce the high pressure fire. Different from the mechanism of high pressure fire, the fuel injection signal is directly controlled by PCM. For this purpose, in addition to the need for a reference signal (18x) and a fuel synchronization signal (camshaft signal), the PCM also receives a fuel control reference signal from the ICM (calculated according to the 3x and 18x signals) so as to provide the fuel injection signal to the injector. Check ICM, camshaft speed sensor, crankshaft speed sensor and its circuit. Check the wiring harness plug of the ICM with the test lamp, and the test light is not lighted, indicating power interruption. Refer to the circuit diagram, and know that the power supply of the injector and ICM is 15 power supply. Check the related fuse, no problem. The 12V voltage is supplied directly to the pink / red conductor (power cord) of the injector wire harness plug, and the engine is started and run. After 3 min, idling gradually jitter, pink / red conductor heating is serious, indicating short circuit fault. Check the injector wire harness, there is no short circuit phenomenon. Referring to the circuit diagram, we know that the pink / red conductor is also the power supply line of the fuel pump. Doubting the poor performance of the fuel pump, the fuel pump relay was pulled off (near the radiator), and a wire with 10A fuse was used to cross the relay's terminal 30 and No. 87, and the fuse was quickly fused, indicating short circuit of the fuel pump. Replace the fuse in the rear part of the fuel pump and the right headlight, and remove the trouble completely. The troubleshooting of this case is that the fuel pump is not completely damaged, but the working current is out of limit, and the fuse gradually becomes hot and fuses. The maintenance experience shows that the control module sometimes does not generate the fault code when the performance of the actuator is bad or the power supply is poor, and the difficulty of maintenance is increased accordingly. The fuse fused in this case is used to provide working voltage to ignition control module, fuel injector and fuel pump. Using analog power supply can quickly find the cause, but if you know the relevant circuit, it is not recommended, otherwise it will cause damage to PCM and ICM.

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