A Dongfeng Peugeot 307 car with a mileage of about 25 thousand km. After repairing the traffic accident, the engine fault lights, ABS lights, parking brake lights and STOP lights on the dashboard often shine, and the odometer is not working. The vehicle has been overhauled at several maintenance plants, and it is impossible to find out the cause of the failure. The testing equipment can not communicate with the ABS control unit. Fault diagnosis: first ask about the car accident and repair process, because this can provide a lot of useful information for maintenance work. In many cases, there is no problem before the accident. Most of the problems after repair are caused by carelessness in the maintenance process. The car is damaged by the left front collision and the ABS pump is damaged. The new pump is being replaced. The damage degree of the car is not serious, and there is no operation for wiring harness and electrical plugs. Will the replacement of ABS pump do not match the model. Let the owner find the ABS pump of the original vehicle for comparison. From the look, there is no difference between the two pumps. The ABS pump of the original car is only damaged by the control unit shell, and there is a mechanical damage of a two-way diode. It is possible to repair it completely. After finding the same type of bidirectional diode welding, the ABS pump will be installed back to the trial run, and the ABS lamp, brake lamp and STOP lamp will normally be extinguished. The odometer can also work normally. It is thought that the fault has been satisfactorily solved. During the trial run, the serious braking deviation of the vehicle was found during the emergency braking. ABS is normal. Why does it suddenly lose the brake? While braking deviation, it is obvious that the brake pedal has a strong foot feeling (this is the result of ABS). Theoretically, one of the most significant functions of ABS is to prevent braking deviation effectively. It seems to be a paradox. So where does the problem come out? First of all, try to exhaust the ABS, without any improvement. Calm down and reanalyze the problem. If the ABS electric control part fails, the ABS light will light up to prompt the driver. There are several possible problems in mechanical parts: one is the failure of the ABS pump; the two is a brake wheel cylinder malfunction; the three is the system has gas; four is the pipeline blockage. According to the situation, none of these possibilities exists. Then there is a possibility that it is not easy to appear, that is, the position of the brake oil pipe is wrong. ABS pump body has a total of 6 tubing locations, MC1, MC2, RD, RG, VC, VD. Among them, MC1, MC2 are the input pipes for the brake master cylinder; RD, RG are rear wheel output; VC and VD are front wheel outputs. After comparison, it was found that two tubing were faulty, and the malfunction was removed according to the correct location.