A driving range of about 126 thousand km, carrying 4.4L V8 engine, and equipped with the ZF company produced by the type 6HP-26 hand self transmission of the 2007 Land Rover found 3 off-road vehicles. The car was first used in the mining area, when the engine speed was high and the actual speed was not very fast. The speed was improved by the engine speed (in fact, there was no high-speed gear), and a long distance journey was carried out with a fault. This results in a mismatch between engine torque and transmission ratio, resulting in engine damage due to high temperature. After overhauling the engine, it was unable to speed up and idling, and so reluctantly moved to another specialized plant. After inspection, it was found that the three element catalyst was seriously blocked, but the automatic transmission could not reach the highest gear after replacement, and then the 4 transmission was continuously changed to finish programming. The result was the same. In this case, we come to another transmission special factory to get the concrete failure of the technician road test. The maximum speed of the engine speed can rise to 4 gear when the engine speed is not more than 1500 to 2000r/min. If the engine speed is higher than 2000 ~ 2500r/min, the speed of 1 litres and 2 gears will be 3500 to 4000r/min at the engine speed. Complete switching, 2 liter 3 gear engine speed in 6000 ~ 6500r/min to complete switching, 3 liter 4 gear engine speed also should be around 6000r/min to complete the switch, while 4 liter 5 gear engine speed is also to complete the switch around 5500r/min, while 5 liters 6 gear engine speed is also around 5000 to 5500r/ min to complete the switch. But manual mode shift is normal. Fault diagnosis: connecting the VCM to the engine and the transmission fault memory, the engine side displays the fault code: the P0026-72- intake valve controls the electromagnetic valve one circuit range performance (cylinder group 1) mechanical fault, the P0028-72 intake valve controls the mechanical malfunction of the solenoid valve, the brake card is in the card position (cylinder group 2), and there are two faults altogether. Code. The transmission, the distributor, the rear slip differential and other systems have no fault codes. It seems that the rising gear problem of the automatic transmission should be caused by the engine failure. The replacement of the intake control solenoid valve in the subsequent maintenance is invalid, and the timing check is opened, correct and correct. When the timing electromagnetic valve seat is opened, it is found that the seat and the timing tooth connection is badly damaged, and the real reason is the filter net on the seat of the timing valve seat when the engine is overhauled. The shape ring is not installed (it should be artificial leakage), after reinstallation, the fault is cleared. At the same time, the engine and the transmission self-adaptive back road test is cleared, the engine is normal (the fault code is not reproduced), but the gearshift fault still exists. It is also related to the engine load, continue to check, test in the case of no load (the lift is not correct in fact) and not high speed gear, which basically shows that the high speed gear can not be changed to the real power of the engine. Again, the engine torque can be read by the engine, the engine torque can reach about 300N m when the engine is 4500r/min, but the other car without fault is tested, the engine speed is about 2500r/min, and the engine torque is about 250N. M, the 6 gear is all up. It seems that the lift condition has little to do with the engine's output torque (in fact, it is directly related, but the knowledge of the technical personnel may not be possible). In the absence of a method, it can only be replaced by the replacement of the related parts, so that a fault free vehicle has been replaced by the transmission assembly, the replacement of the torque converter, the throttle, the gasoline pump, the control module, the whole terrain module, the gear seat, the three element regenerator, the air flow sensor, the post difference speed. Both the motor and the distributor are not able to troubleshoot. The whole vehicle refresh software version is 124.V6.05. In this way, all the changes have been checked, and the inspection has been checked. We can confirm that the transmission body must be normal. The main reference information for the rising gear conditions of the automatic transmission is the engine load information reflected by the throttle (of course the actual engine power must meet the shift condition) and the speed signal of the transmission output part. Then, what is the reason that the transmission can not be changed to the high speed gear? The maintenance was in a deadlock for a moment. In this way, the author participates in the diagnosis process of the vehicle. Because simply from the dynamic data of the system, the problem can not be found directly. Later, guided by engineers from Land Rover China, he still used the contrast test method to find the problem eventually. It is still to look for a scan and contrast of the same data without a malfunction vehicle. The man is not in the mind, and at last there is a difference between the torque calculated by the engine and the transmission to the automatic transmission control unit. Under the condition of 25% to 40% throttle opening, the torque of the engine should be around 200 ~ 250N m. The information of the fault car is obviously wrong. The engine torque of the engine is about 150 to 180N m under the opening of the 25% to 40% throttle, and the engine speed reaches to about 4000 to 4500r/min. At about 250 ~ 300N / m, it is obvious that the relationship between the engine speed and the torque is wrong (in fact, the original repair technician has found this). Therefore, in this case, the automatic transmission control unit is wrong with the transmission of the load information through the network through the engine control unit, which affects the rising gear process of the automatic transmission. Considering that more input information is in the normal range and replace so many parts, only the engine control unit is the most likely (data calculation error), and the final replacement of the engine control unit fault can be eliminated. Fault summary: from this case, we have learned a lot of lessons, deeply aware of the relationship between engine torque and automatic transmission ratio switching, of course, at the shift point everyone will know that the engine has torque reduction control when the transmission ratio is switched from large to small (rising gear); in turn, the transmission ratio is switched from small to large. The engine is in the process of increasing torque control. However, the automatic transmission will not make a rise in the control unit even when the engine torque is not up to the requirement of the lift (conditions are not satisfied) while the engine is not satisfied. Therefore, we should strengthen learning engine torque, power, automatic transmission shift point, transmission ratio and other aspects of knowledge.