With Manufacturer's Scan Tool

Intake manifold change-over, checking

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

- V.A.G 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 vacuum diaphragm for 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.
- Test activation of intake manifold change-over valve -N156- through the output Diagnostic Test Mode (DTM). [1][2]Output Diagnostic Test Mode (DTM), (Function 03)

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 and forth

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