Audi Workshop Service and Repair Manuals

Fitting location

Checking intake manifold changeover solenoid valve -N156

• ‒ Allow engine to idle for 2 to 3 minutes to build up vacuum.
• ‒ Switch off engine.
• ‒ Switch on ignition.

Solenoid valve must be felt and heard to click. Final control diagnosis is terminated after one minute.

• ‒ Switch off ignition if solenoid valve does not click.

• ‒ Unplug connector from intake manifold changeover solenoid valve -N156.
• ‒ → Measure resistance with V.A.G 1526 between solenoid valve contacts.

• Specification: 25...35 ohms

• ‒ If reading does not match specification, replace intake manifold changeover solenoid valve -N156.

If reading matches specification, check power supply => Page 24-124.

Checking power supply of intake manifold changeover solenoid valve -N156

• ‒ → Connect diode test lamp V.A.G 1527 with leads from adapter set V.A.G 1594 to socket 1 of connector and engine earth.
• ‒ Briefly operate starter.

Diode test lamp must light.

• ‒ If diode test lamp does not light:
• ‒ Check fuse for intake manifold changeover solenoid valve:

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

If fuse is OK:

• ‒ Check for open circuit/short circuit in wiring from socket 1 of connector via fuse for intake manifold changeover solenoid valve to fuel pump relay.

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

If power supply is OK, check actuation => Page 24-125.

Checking actuation of intake manifold changeover solenoid valve

• ‒ Connect diode test lamp V.A.G 1527 with leads from adapter set V.A.G 1594 to sockets 1 (positive) and 2 of connector at intake manifold changeover solenoid valve.

If diode test lamp does not flash or if it is permanently lit: Check wiring.

Checking wiring

• ‒ Connect test box V.A.G 1598/31 to engine control unit wiring harness. Actual engine control unit is not to be connected.

Check for short to positive/earth and open circuit in the following wiring.

• Resistance: max. 1.5 ohms

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

• ‒ If wiring is OK, replace engine control unit .
• ‒ Check operation of intake manifold changeover -N156 again
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