Checking intake manifold changeover solenoid valve -N156 — AUDI
Checking intake manifold changeover solenoid valve -N156 on Audi: factory workshop procedure for engines AKC, APG, AQF, AQG.
Workshop procedure for AUDI — the factory write-up, straight from real workshop data.
📋 Procedure
AQF AQH ARU AKC AUW AVN AVP
Run engine at idling speed for 2 or 3 minutes to build up vacuum pressure.
Switch engine off.
Switch the ignition on.
Perform final control diagnosis and activate intake manifold changeover solenoid valves =>Page
01-72.
Final control diagnosis
⇒
Intake manifold changeover valve
-N156
Indicated on display:
The valve should click (clicking can be heard and felt). After 1 minute the final control diagnosis is terminated.
If the solenoid valve does not click:
Switch ignition off.
Detach connector from relevant solenoid valve for intake manifold changeover solenoid valve.
Measure resistance between the solenoid valve contacts using V.A.G 1526.
Specified value: 25...35 Ohms
If the measured value is not as specified, renew the solenoid valve for intake manifold changeover solenoid valve.
If the specified value is achieved, check the voltage supply.
Checking voltage supply of intake manifold changeover solenoid valve
Connect diode test lamp V.A.G 1527 between engine earth and socket 1 (positive) on connector using cables from adapter set V.A.G 1594.
Operate starter briefly.
The diode test lamp should illuminate.
If the diode test lamp does not illuminate:
Check fuse for solenoid valve for intake manifold changeover solenoid valve.
=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
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 change-over solenoid valve.
=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
If the voltage supply is OK, check actuation.
Re-insert the fuel pump relay and fuse.
Checking actuation of intake manifold changeover solenoid valve
Connect diode test lamp V.A.G 1527 between sockets 1 and 2 on connector for intake manifold changeover solenoid valve using cables from adapter set V.A.G 1594.
Perform final control diagnosis and actuate relevant solenoid valve for intake manifold changeover solenoid valve => Page
01-72.
Final control diagnosis
⇒
Intake manifold changeover valve
-N156
Indicated on display:
If the diode test lamp does not flash or is continuously lit: Check the wiring.
Checking wiring
Connect test box V.A.G 1598/31 to wiring harness for engine control unit; do not connect the engine control unit => Page
24-12.
Check the following wiring connections for open circuit and short circuit to positive or earth.
Intake manifold changeover connector 1 -N156 / socket · Test box V.A.G 1598/31 socket
2 · => Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
Wire resistance: max. 1.5 Ohm
=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
If the wiring is OK replace engine control unit => Page
24-16.
Check intake manifold changeover valve again for function =>Page
24-135.
TorqFix answers live for your specific car — tell it the engine code and it serves the matching sequence, torque figures and wiring for that exact variant.
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Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.
Seen a figure that does not match your manual? Write to us — we correct it and note when. support@torqfix.com
The story behind TorqFix → · How these pages are made →Workshop data on this page last updated 20 Sep 2026.