Model: Hongyan Jieshi
Engine model: Shangfei red C11
Emission standard: Guosi
Computer version model: edc17cv44
Fault phenomenon: the engine fault light is on and the power is insufficient.
Fault code: p1405 dm1dcu can signal receiving timeout
1. DCU is not powered on or DCU is damaged.
2. The can line is blocked.
1. Use the diagnostic instrument to enter the DCU to read the data stream. It is found that many data streams are not supported, as shown in the following figure of dcu communication.
2. Since the diagnosis can be entered but the data display is not supported, it is suspected that it is a problem with the diagnostic instrument. Communicate with the engineer and there is no development defect in this system of dcu communication .
3. In a skeptical attitude, the diagnostic results of other brands of diagnostic instruments are the same. The data flow also shows that it is not supported. The problem must be in the car.
4. To repair the can line fault, the CAN node fault analysis of the diagnostic instrument is a sharp tool for maintenance. Using the CAN node fault analysis function, it is found that the DCU node can be scanned, as shown in the figure.
5. Since the CAN bus analysis function can scan DCU, it means that there is DCU ID number and data transmission on the bus of dcu communication .
6. This vehicle is equipped with Kailong DCU + Kailong urea pump, and the Kailong urea pump and DCU are connected to the main can line together. This ID number may be sent by the urea pump. Disconnect the urea pump and scan the can line again, and the DCU node on the CAN bus disappears, as shown in the following figure.
7. According to the test results, the fault point is very clear. It is the DCU itself. Disconnect the DCU plug and find that the DCU plug is corroded by water. After replacement, the fault is solved, as shown in the following figure of dcu communication .
The fault point of this case is really easy to find. Sharing this maintenance process is mainly to share the use method of a diagnostic instrument and how to use various functions of diagnosis.
1. When using the CAN bus analysis function for the first time, it may be misled by the scanned results. Therefore, as users, they should learn to analyze. In this case, DCU and can line urea pump belong to post-processing components, and the assigned ID numbers are the same. If you understand this truth, it will be easy to solve this kind of fault.
2. When using this function, it is clear that the engine ECU has been unplugged, but the engine ECU ID number is still on the CAN bus, which is the data sent by other ECUs on behalf of ECU.
3. The CAN bus analysis function can not only scan the number of CAN bus nodes, but also diagnose each node, read code, clear code and read data flow. It can be used as an alternative function for diagnosis.