A Chevrolet 80km 1.6L car that runs only mileage. Owners reflect: the engine fault lights of the car are lit, and the accelerator pedal is strong, but the acceleration of the vehicle is not obvious. The owner bought a car for two days, and the engine failure lamp on the meter suddenly lit up, and the automatic transmission didn't lift. Check the transmission without oil leak marks, use GDS2 to check the engine control module has fault code (transmission control module has requested light fault indicator light), the transmission control module has fault code (pressure control solenoid valve 2 card stagnation). Try to delete the fault code, test run 2km or so, fault reappearance, automatic transmission into the emergency mode, restricted to reverse gear and 2 block, no lifting gear. Check the maintenance manual that clutch pressure control solenoid valve 2 is part of the control solenoid assembly, there is no repairable components. The pressure control solenoid valve 2 regulates the transmission oil pressure to the 3-5 / reverse control valve to control the oil pressure supplied to the 3-5 / reverse clutch. The transmission control module calculates the transmission ratio based on the speed signal transmitted by the input axis speed sensor (ISS) and the output axis speed sensor (OSS), and compares the transmission ratio with the transmission ratio expected by each instructed shift. When the instruction 3-5 gear / reversing clutch joins the continuous 3S and the speed of the transmission input shaft is greater than the desired input shaft speed 400r/min, the transmission control module detects the clutch transmission ratio is wrong or suddenly increases, this case appears 3 times the fault code P0776, because it is a class fault diagnosis code, TCM will take The following operation: the transmission control module commands the maximum pressure of the pipeline; the transmission control module limits the transmission to the inverted and 2 gear; the transmission control module freezes the adaptive function; the transmission control module disables the touch off / gear shift function; the transmission control module disables the forward shift shift. The possible reasons for the failure are: (1) the control valve assembly 3-5 gear / reversing valve caused by clash, bond, valve damage or hole scratching cause jam / sluggish, control the unidirectional ball valve in the valve body because the debris is not right in place; and control the pressure of the solenoid valve assembly to control the leakage of the O type seal ring of the solenoid valve 2; (3) 3-5 gear / reverse gear and 4-5-6 Clutch clutch housing assembly 3-5 / reverse clutch bottom plate clasp is not in place, resulting in clutch assembly overrun. According to the maintenance principle of "from the form to the inside, from the simple to the complex", it is decided not to disintegrate the transmission. The module side cover of the transmission is dismantled and the control of the solenoid valve assembly (with the valve and the transmission control module) is replaced, and the failure of the TCM maintenance program is eliminated.