Testing intake manifold change-over valve — AUDI

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

Final control diagnosis
⇒
Intake manifold press. change valve -N156
Perform final control diagnosis and activate intake manifold change-over valve
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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 valve contacts using V.A.G 1526.

Specification: 25...35ω

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

If the reading matches the specification, test voltage supply.

Testing voltage supply to intake manifold change-over valve

-N156

Connect diode test lamp V.A.G 1527 between engine earth and contact 1 on connector using test leads from auxiliary cable 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.

If the fuse is OK:

Test for open circuit and short circuit in wiring between fuel pump relay and contact 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.

Testing activation of intake manifold change-over valve

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

Final control diagnosis
⇒
Intake manifold press. change valve -N156
Perform final control diagnosis and activate intake manifold change-over valve
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If the diode test lamp does not flash or lights up continuously, test the wiring.

Testing wiring

Connect test box V.A.G 1598/22 to wiring harness for engine control unit
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Test wiring between contact 2 on connector for intake manifold change-over valve...
...and contact 64 on engine control unit for open circuit and/or short circuit.

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

Connector for intake manifold change-over · Socket on test box V.A.G 1598/22
2 · 64

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