Audi Workshop Service and Repair Manuals

Checking valve for obstructions and leaks

• ‒ Remove intake manifold change-over valve.
• ‒ Reconnect valve to wiring harness.

• ‒ While the final control diagnosis is running, blow through the valve connection to check whether the valve is opening and closing properly.

If the valve does not open and close:

• ‒ Renew intake manifold change-over valve.

If no faults have been found in any of the tests so far:

• ‒ Re-install intake manifold change-over valve.
• ‒ Test vacuum system for leaks => Page 24-129

Testing vacuum system for leaks

• ‒ Run engine at idling speed for 2 or 3 minutes to build up vacuum pressure.
• ‒ Switch off ignition.
• ‒ Unplug connector from intake manifold change-over valve -N156.
• ‒ → Connect one of the contacts on the solenoid valve to engine earth using test leads and crocodile clamp from V.A.G 1594.

• ‒ → Connect the second contact on the solenoid valve to positive using remote control V.A.G 1348/3A, adapter lead V.A.G 1348/3-2 and an auxiliary cable.
• ‒ → Operate remote control V.A.G 1348/3A for about 2 or 3 minutes. During this time the vacuum unit should remain in the "pulled-in" position.

If the vacuum unit returns to its original "rest" position, carry out the following test:

• ‒ Disconnect vacuum hose from vacuum unit for intake manifold change-over system.
• ‒ → Connect hand-held vacuum pump V.A.G 1390 to vacuum unit.
• ‒ Operate hand-held vacuum pump and check whether change-over function is working.
• ‒ Test vacuum unit for leaks. (The vacuum unit should not return to the "rest" position while a vacuum is being maintained via the hand pump.)

If the vacuum unit returns to its "rest" position:

• ‒ Renew vacuum unit.