Does the questioner want to ask “How to understand the power-on process of Great Wall Fengjun 5ECU through the circuit diagram”? The steps are as follows:
1. First, when the key switch is in the T15 position, pin K88 of the ECU receives 24V voltage from the power supply, telling the ECU that it should be powered on.
2. Then determine whether the ECU is powered on successfully or the ECU is normal. Once the ECU is turned on, the corresponding pin will produce voltage. Measure whether the output voltage is normal. Basically determine whether the ECU is powered on successfully or the ECU is normal. Pins generally measured include communication pins (normally the CAN line is around 2.5V and the K line is slightly smaller than the supply voltage), public high end (normally 24V or 12V ), the power module (normally 5 V), and the tepower supply of the metering device (normally (24V or 12V), just measure the voltage of the corresponding pin.
3. After the final power-on is successful, when the car key is turned to START position, the start switch T50 is closed and K35 will receive the 24V voltage when the ECU detects this voltage, it will lower the voltage K71, let the start relay engage, the starter circuit is connected. , the T50 will open under the action of spring force and the engine start is completed
When Great Wall Fengjun turns on the ignition switch, the oil pump relay will not turn on. does not close.
The oil pump cap is off, and the fuse and relay are fine. It is a wiring problem
.Check the circuit from the power supply to the fuel pump plug for a break. If the break is not large, it is likely.some wires are exposed and tied up. to the chassis. This may cause insufficient current and cause the vehicle to stop. This situation can occur when the line is running or the set of lines is pulled by something or a component a short distance, so that the core of the line. is not completely disconnected and the skin is not broken. There may also be a problem with the car's computer board.
Check two places. First, check if the relay coil is still connected; secondly, check whether there is electricity in the power source, positive and negative polarity, etc.
If the relay does not close, first check whether its coil is normal, because the coil has a corresponding resistance value. At this point you can use a multimeter to measure it. If the resistance value is relatively large or 0, it means that the coil has been damagedaged. At this point a new relay needs to be replaced. If the relay is not energized, then you need to find a way to eliminate the cause of the circuit, so that the electrical relay will close naturally after being energized.