Intake Manifold: Testing and Inspection

This test should only be performed if there is a loss of power.
The intake manifold switches from the long intake path to the short one at approx. 4700 RPM.

Special tools and equipment
- VAG 1551 Scan Tool (or VAG 1552 mobile scan tool) with VAG 1551/3 cable
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 connector test kit







- VAG 1390 Hand Vacuum Pump

Functional Test
- Start engine and let run at idle.
- Increase engine speed clearly above 4700 RPM. This process should actuate the vacuum diaphragm for the intake manifold change-over. (Component location: on intake manifold front left, beneath ignition coils).

If the change-over does not occur, the following tests should be performed.
- First, test the activation of the intake manifold change-over valve (N156) through the output Diagnostic Test Mode (DTM). Testing and Inspection

If the activation appears to be in order:
- Connect Scan Tool (ST) or vehicle system tester.







- Disconnect vacuum hose (1) from check-valve (2) and connect hand vacuum pump VAG 1390 to disconnected hose.







- Perform output Diagnostic Test Mode (DTM) again. If intake manifold change-over valve is activated, uniformly operate hand pump.
- The setting element must, between the two positions, switch back arid forth.

If the change-over does not function as described:
- Check whether the change-over mechanism moves easily. To do this, operate the linkage by hand.
- Check whether the vacuum lines are correctly connected.
- Check whether the vacuum system, including the vacuum reservoir in the left wheel well, is properly sealed.