Charge air pressure bypass valve, testing

NOTE:

The charge air pressure bypass valve is located upstream of the turbocharger. It is opened by vacuum from the electrically operated air recirculation valve for turbocharger (-N249-) when the engine is on overrun or under part load or when idling. This disperses the pressurized air (charge air pressure) upstream of the throttle valve, and thus keeps the turbocharger rotating at a higher speed.
Check the air recirculation valve if the engine is not producing full power, or jerking when the throttle is opened and closed.

Special tools, testers and auxiliary items

Fig 1: Identifying Hand Vacuum Pump V.A.G. 1390

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Test sequence

Fig 2: Connecting Vacuum Pump V.A.G 1390 To Charge Air Pressure Bypass Valve

Courtesy of VOLKSWAGEN UNITED STATES, INC.

If the charge air pressure bypass valve does not open and close as specified, or if the valve plate does not seal properly when the valve is closed:

Replace the charge air pressure bypass valve. Secure the connections on the valve with screw-type clips.