What is the reason why the automatic transmission suddenly does not upshift?

The following are several reasons why the automatic transmission does not upshift: 1, the throttle cable or throttle position sensor is improperly adjusted: the fault can be solved by checking and adjusting the throttle cable and throttle position sensor. 2. Vehicle speed sensor failure: Check the vehicle speed sensor and replace it. 3. The shift valve is stuck or the gear switch is faulty: check the gear switch signal. If there is no fault in the control system, disassemble the automatic transmission. The following is the introduction of automatic transmission: 1. Automatic transmission must be filled with automatic transmission oil specified by the manufacturer. Automatic transmission must not add manual transmission gear oil, main reducer special oil or engine oil by mistake, otherwise all clutches and brakes will be seriously ablated after driving for a period of time. 2. The automatic transmission oil should be changed in time. When changing the automatic transmission oil, clean the crude oil as much as possible. The automatic gearbox should strictly control the fuel quantity. Clean the clutch and brake in time after ablation. The hydraulic system of the torque converter has two oil inlet holes, one at the bottom of the control valve body.