A Passat B4 sedan, equipped with AG401M automatic transmission, the user reflects the car in the normal high-speed driving when the engine idling phenomenon.
    After receiving the car, the maintenance personnel first replaced the mass-specific transmission oil and filter. After the road test, the fault phenomenon without any change, and the basic confirmation of the fault for the 2 block up 3 block slightly slippery, 3 block up 4 block serious slip.
    Maintenance personnel first use the fault diagnosis instrument V.A.G1552 on the transmission electronic control system was detected, and in the transmission control unit fault memory found "01192 - hydraulic torque converter mechanical failure" fault code. To clear the road after the road test, the results of 01192 fault code again. On the 01192 fault code analysis, set the fault code is the condition of the torque converter lock clutch slip speed beyond the control unit set the limit value. The operation of the torque converter lock-up clutch is such that when the control unit receives a clutch-lock clutch engagement condition, the control unit locks the control solenoid valve N91, The slide valve enters the torque converter lock-up clutch, and the same speed should be formed between the pump wheel and the turbine of the torque converter to achieve a rigid connection between the engine and the transmission. When the control unit sets the fault code, we should focus on checking the working performance of the N93 solenoid valve (solenoid valve test stand), the hydraulic control valve body lock control valve (valve body test machine) and torque converter itself. Of course, in exceptional circumstances, if the K3 clutch slips, it will also cause the lock slip to rise, because the K3 clutch is the turbine (connected by the K3 shaft spline to the turbine). So K3 clutch work will lead directly to the torque converter lock conditions. So, when we are troubleshooting, once encountered 01192 fault code, can not only consider the torque converter lock control problem.
    Transmission 3 block up 4 block slip should be 4 block (speed) actuator abnormal operation, electronic control system command error, and hydraulic control system, shift solenoid valve and control oil pipeline leakage phenomenon. Through the shift actuator worksheet (table), we can see that the speedpiece actuator is K3 (3/4 gear clutch) and B2 (2/4 brake). According to the working principle of the transmission control system, it can be seen that the shift solenoid valve N90 controls the K3 clutch, the N89 controls the B2 brake and the B2 brake is the common component of the 2,4 block. As the transmission in the implementation of 1 block up 2 block when there is no slip phenomenon, indicating that the B2 brake will not be a problem, then most likely K3 clutch itself or control system problems. As the K3 clutch is 3,4 block of the common components, 3 gears 4 block slip slip and 2 block 3 block slip slightly reason is that the 3 block for the direct block K1 (1/3 clutch) clutch and K3 clutch at the same time work , 4 block for the overspeed, K3 clutch at this time must be as active components appear. If the electronic control unit issues the overspeed command is correct, then the problem should be in the shift solenoid valve, the hydraulic valve body and the hydraulic circuit and the actuator K3 itself. To verify whether the problem lies in the electronic control system or hydraulic mechanical system, we control the shift solenoid valve to perform 4-block state, to see whether the transmission can achieve ultra-speed gear. The results of 3 block up 4 block is still slippery, so had to break the automatic transmission.
    After decomposing the transmission, we found that the K3 clutch was seriously burned and the other oil components were good, so it was decided to check the K3 clutch and its control circuit. K3 clutch can use compressed air to verify its performance, by carefully checking the K3 clutch and control the oil circuit, and did not find any problems, indicating that the cause of burning K3 clutch should be based on the hydraulic control valve body pressure, it should Focus on the K3 control valve and N90 solenoid valve in the valve body.
    Replace the K3 assembly by refurbishing the torque converter, replace the hydraulic control valve body and replace the shift solenoid valve N90 and all the sealing components.