With Manufacturer's Scan Tool

Intake Manifold Tuning (IMT) Valve -N156-, Checking

- Perform check only if performance is poor.
- The intake manifold change-over from long to short intake ports occurs at approx. 4000 RPM.

Special tools and equipment
- VAG1551 Scan Tool (ST) or VAG1552 mobile scan tool with VAG1551/3 adapter cable







- VAG1390 hand vacuum pump
- Multimeter (Fluke 83 or equivalent)
- VW1594 adapter set

Checking function
- Start engine and run at idle.

The change-over barrel in intake manifold is positioned at short passageway.
- Fully depress accelerator pedal, then release before 4000 RPM.







The actuating element must rotate the barrel in the intake manifold (arrow).

If the positioning element does not perform the change-over sequence:
- First check activation of Intake Manifold Tuning (IMT) valve -N156- via output Diagnostic Test Mode (DTM).

If the activation is OK:
- Connect scan tool or vehicle test system.







- Disconnect vacuum hose -1- from Intake Manifold Tuning (IMT) valve - N156- -2-.
- Connect VAG1390 hand vacuum pump to Intake Manifold Tuning (IMT) valve -N156- -2-.







- Perform output Diagnostic Test Mode (DTM) again. When Intake Manifold Tuning (IMT) valve -N156- is activated, operate hand pump uniformly.
The positioning element must switch back and forth between the two positions.

If the change-over does not function as described:
- Check change-over mechanical components for ease of movement (move rods by hand).
- Check that vacuum hoses are connected correctly.
- Check vacuum system, including vacuum reservoir.


NOTE: The vacuum reservoir is bolted to the sump on the left-side, next to the oil filter.