Audi Workshop Service and Repair Manuals

Fitting location .

Testing intake manifold change-over valve -N156

• ‒ Run engine at idling speed for 2 or 3 minutes to build up vacuum.
• ‒ Switch engine off.
• ‒ Switch ignition on.

The valve should click (clicking can be heard and felt). After 1 minute the final control diagnosis is terminated.

• ‒ If the valve does not click, switch off the ignition.

• ‒ Unplug connector from intake manifold change-over valve -N156.
• ‒ → Measure resistance between contacts of solenoid valve using V.A.G 1526.

• Specification: 25...35 ω

• ‒ If the reading does not match the specification, renew intake manifold change-over valve -N156.

If the reading matches the specification, test voltage supply
=> Page 24-125.

Testing voltage supply to intake manifold change-over valve

-N156

• ‒ → Connect diode test lamp V.A.G 1527 between engine earth and socket 1 on connector using test leads from auxiliary test set V.A.G 1594.
• ‒ Operate the starter briefly.

The diode test lamp should light up.

• ‒ If the diode test lamp does not light up:
• ‒ Test fuse for intake manifold change-over valve.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

If the fuse is OK:

• ‒ Test 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.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

If the voltage supply is OK, test activation. => Page 24-126

Testing activation of intake manifold change-over valve

• ‒ Connect diode test lamp V.A.G 1527 between sockets 1 (positive) and 2 on connector for intake manifold change-over valve using test leads from auxiliary cable set V.A.G 1594.

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

Testing wiring

• ‒ Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
  => Page 24-10.

Test the following wiring connections for open circuits and short to positive or earth.

• Resistance in wiring: max. 1.5 ω

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

• ‒ If the wiring is OK, fit a new engine control unit
  .
• ‒ Test operation of intake manifold change-over valve -N156 again
  .