Symbol 408 reports the intake tolerance.

When the car is idling, the intake pressure is generally between 27 and 30 kPa. The intake pressure sensor is used to detect the intake air of the engine and control the basic fuel injection quantity. If this sensor is broken, and the computer can't receive the intake air, the mixture will be too thick and too thin, leading to black smoke, incomplete combustion, and even shooting of the exhaust pipe. The mixture will lead to insufficient fuel, backfire, insufficient power, weak acceleration and even difficult start. The intake manifold pressure is more accurate, that is, the absolute pressure of the intake manifold, which is generally between 40 and 40-80 kPa. When the engine is working, the intake manifold pressure will be lower than the atmospheric pressure under the suction formed by the downward movement of the piston in the intake stroke. Intake manifold pressure will be affected by throttle opening, engine speed and sealing performance. The smaller the throttle opening, the greater the suction effect of the piston, the greater the intake manifold suction, the greater the vacuum degree, the lower the intake manifold pressure, the higher the engine speed, the greater the suction effect of the piston, the greater the intake manifold suction, the greater the vacuum degree, the lower the intake manifold pressure, the better the sealing performance, the greater the intake manifold suction, the greater the vacuum degree and the lower the intake manifold pressure.