Change-Over Valve N156 & Intake Tuning (IMT) Valve 2 N261 Check

Intake Manifold Change-Over Valve -N156 and Intake Manifold Tuning (IMT) Valve -2- -N261, Checking

Checking Intake Manifold Change-Over Valve -N156 and Intake Manifold Tuning (IMT) Valve -2- -N261

- Run engine at idling speed for 2 or 3 minutes to build up vacuum.
- Switch engine off.
- Switch ignition on.
- Perform output Diagnostic Test Mode (DTM) and activate solenoid valves for intake manifold change-over. Refer to Scan Tool Testing/Output Diagnostic Test Mode (DTM) (Function 03) Testing and Inspection

Indicated on display


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


Indicated on display


Output Diagnostic Test Mode ->
Intake manifold tuning valve 2 -N261







The valves should click (clicking can be heard and felt). After 1 minute the DTM is terminated.

If one of the valves does not click.
- Switch ignition off.
- Disconnect harness connector from relevant intake manifold change-over solenoid valve.







- Measure resistance between valve contacts using Fluke 83 (or equivalent) multimeter.

Specification: 25 to 35 ohm

- If reading does not match the specification, replace intake manifold change-over valve.

If the reading matches the specification, check voltage supply.

Checking voltage supply to intake manifold change-over valve







- Connect VAG1527B diode test lamp between engine Ground (GND) and socket 1 on connector using test leads from VAG1594 connector test kit.
- Operate starter briefly.

The diode test lamp should light up.

If diode test lamp does not light up:
- Check fuse for intake manifold changeover valve.

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

If the voltage supply is OK, check activation.

- Re-install fuel pump relay and fuse.

Checking activation of intake manifold change-over valve
- Connect VAG1527B diode test lamp between sockets 1 (B+) and 2 on connector for intake manifold change-over valve using test leads from VAG1594 connector test kit.
- Perform output Diagnostic Test Mode (DTM) and activate relevant intake manifold changeover valve. Refer to Scan Tool Testing/Output Diagnostic Test Mode (DTM) (Function 03) Testing and Inspection

Indicated on display


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


Indicated on display


Output Diagnostic Test Mode ->
Intake manifold tuning valve 2 -N261


If diode test lamp does not flash or lights up continuously, check wiring.

Check wiring
- Connect VAG1598/31 test box to wiring harness for engine control module. Do not connect to the engine control module itself. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG1598/31 Test Box" Testing and Inspection







Test the following wiring connections for open circuits and short to B+ or Ground (GND).

Connector for VAG1598/31 test
intake manifold box, socket
change-over 1, socket
2 104

Connector for VAG1598/31 test
intake manifold box socket
change-over 2, socket
2 45

Resistance in wiring: max. 1.5 ohm.

If wiring is OK.
- Replace Engine Control Module (ECM).
- Check intake manifold change-over function again.
- Display readiness code. The readiness code must be regenerated if the DTC memory was erased.
Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Readiness Code" Testing and Inspection
Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Generating Readiness Code" Testing and Inspection