Yusheng s350 diesel four-wheel drive, in the two-wheel drive state, the four-wheel drive lights, sideslip lights, and ABS lights are all on. The first time this happened was when climbing a large cross-axis slope, just restart the ignition. This time, it turned on for some reason when driving in the snow, and it will disappear after restarting, but it will still light up for a short time, and it will not disappear after restarting slowly, and it will turn on when the ignition is turned on. Went to a friend’s car repair place to check that the right rear wheel speed sensor was open. He judged that the sensor was damaged, and the fault was not eliminated after buying and replacing. He had no choice for the time being. He said that the main line might be broken, so he asked me to go to the 4S shop to check it. Haha, it seems that I should do it myself.
I came back and began to check the information carefully, and found all the wiring harness paths, plug wiring sequences and colors from the ESP module in the engine compartment to the sensor. Unplug the relay plugs between the wiring harnesses from the esp one by one, short-circuit one end, and test the other end section by section with a multimeter. It is found that the branch of the chassis wiring harness from the left front door to the rear axle and the right rear sensor branch is blocked. The lights went out immediately. The cause of the disease was found, and the treatment was easy to talk about. I planned to save trouble and find out the fault point and welded it. Later, I decided to replace the insurance with a new one. But to change the wiring harness, the fuel tank must be removed. My fuel tank has just been filled with oil! When the fault light is on, the four-wheel drive cannot be loaded. If there is no four-wheel drive, I dare not go out to play. When will I run a tank of gas in the city without going out? Pump oil, do it, bought two 30-liter plastic barrels, and spent about an hour changing the wiring harness with the little master, and the symptoms were eliminated. It’s just a little troublesome to work, nothing else.
Pumping oil, I didn’t expect diesel to be light green, just like soda, haha
It’s over if it can’t be repaired, you must find the fault point of the disconnection! Take the cable back, the multimeter test is still open circuit on the right side, and the plugs at both ends are fine. Start to use a sharp multimeter pen to test through the plastic skin section by section, and it is easy to find the fault point that is almost disconnected. How can a good line be broken? What is the shape of the broken end? It is not clear to the naked eye, but observed under a microscope, the multi-strand copper wires have been severely corroded and broken, and the plastic outsourcing has also hardened. Fortunately, there is no troublesome in-situ soldering, which is more troublesome.
Breakpoint found directly.
The broken ends under the microscope are all rusted, and the soil stuffed inside has turned green.
The broken end under the microscope, the other end.
Normal without rusty wires. I truncated it on purpose.
The severed end was very rusted.
The wiring harness looks like.
The fault point, the original fixed point in the red circle, is broken near here.
Cause Analysis and Suggestions
The broken line fault point is located near a fixed point on the frame after the chassis wire harness comes out from the fuel tank, and the next fixed point is on the rear axle. The line between these two fixed points is free, and will bend or stretch. After the vehicle is raised, the free line is a little bit tight. After a long time, the plastic will age and harden, and the line skin near the fixed point on the top may be a little cracked. Then the water goes in. Slowly corroded the copper wire, which should be the cause of the failure. Brothers who are ascending, please pay attention. If necessary, remove a fixed point and make the free line a little longer.