Intake Manifold Change-Over Valve - N156-, Checking

Intake manifold change-over valve - N156-, checking

- Run engine at idling speed for 2 or 3 minutes to build up vacuum pressure.
- Switch engine off.
- Switch ignition on.
- Perform output Diagnostic Test Mode and actuate intake manifold change-over valve. Output Diagnostic Test Mode (DTM) (Function 03)

Indicated on display


Output Diagnostic Test Mode ->
Intake manifold change-over valve -N156-


Valve should click (clicking can be heard and felt). After 1 minute output DTM is terminated.
If solenoid valve does not click:
- Switch ignition off.
- Disconnect connector from relevant solenoid valve for intake manifold change-over.







- Measure resistance between contacts on solenoid valve using VAG 1526.
Specified value: 25...35 Ohms
- If measured value is not as specified, replace solenoid valve for intake manifold change-over.

If the specified value is achieved, check the voltage supply.

Checking voltage supply of intake manifold change-over valve







- Connect diode test lamp V.A.G 1527 between engine Ground and socket 1 (positive) on connector using cables from adapter set VAG 1594.
- Operate starter briefly.
Diode test lamp should illuminate.

If the diode test lamp does not illuminate:
- Check fuse for solenoid valve for intake manifold change-over.

If the fuse is OK:
- Check for open circuit and short in wiring between fuel pump relay and socket 1 on connector via fuse for intake manifold changeover solenoid valve.

If the voltage supply is OK, check actuation.
- Re-insert fuel pump relay and fuse.

Checking actuation of intake manifold change-over valve
- Connect diode test lamp VAG 1527 between sockets 1 and 2 on connector for intake manifold change-over valve using cables from adapter set VAG 1594.
- Perform output Diagnostic Test Mode (DTM) and actuate solenoid valve for intake manifold change-over. Output Diagnostic Test Mode (DTM) (Function 03)

Indicated on display


Output Diagnostic Test Mode ->
Intake manifold change-over valve -N156-


If the diode test lamp does not flash or is continuously lit:
- Check wiring.

Checking wiring
- Connect test box VAG 1598/31 to wiring harness for engine control unit; do not connect engine control module. Connecting VAG 1598/31 Test Box

Check the following wiring connections for open circuit and short circuit to positive or Ground.

Connector for intake
manifold change-over 1 socket Test box VAG 1598/31 socket

2 48

Wire resistance: max. 1.5 Ohm

If wiring is OK:
- Replace engine control module.
- Check intake manifold change-over again for function.
- Read readiness code. Generate readiness code again if DTC memory was erased. Readiness Code, Generating