Audi Workshop Service and Repair Manuals

Special tools,
testers and equipment required

• ◆ V.A.G 1348/3-2
• ◆ V.A.G 1348/3A
• ◆ V.A.G 1390
• ◆ V.A.G 1594 A

• ‒ Run engine at idling speed for 2 or 3 minutes to build up vacuum pressure.
• ‒ Switch off ignition.
• ‒ Unplug connector from intake manifold changeover 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 A.
• ‒ Connect second contact on -N156 to positive using remote control V.A.G 1348/3A, adapter lead V.A.G 1348/3-2 and auxiliary cable.
• ‒ Operate remote control V.A.G 1348/3A approx. 2 to 3 minutes; throughout this period, the vacuum unit should pick up.

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

• ‒ Disconnect vacuum hoses from vacuum unit for intake manifold changeover system.
• ‒ Connect hand pump V.A.G 1390 to vacuum unit.
• ‒ Operate hand pump and check whether changeover function is working.

• ‒ Check vacuum unit for leaks. (The vacuum unit should not return to rest position until the hand pump is vented to atmosphere.)
• ‒ If necessary, renew vacuum unit.
• ‒ If the vacuum unit does not pick up, check -N156 as follows for blockage:

• ‒ → Connect one of the contacts of -N156 to engine earth using test leads and crocodile clamp from V.A.G 1594 A.
• ‒ Connect second contact on -N156 to positive using remote control V.A.G 1348/3A, adapter lead V.A.G 1348/3-2 and auxiliary cable.
• ‒ Operate remote control V.A.G 1348/3A.
• ‒ Check valve for obstructions (remove vacuum hoses and blow through).
• ‒ If necessary, renew intake manifold changeover valve.
• ‒ If no faults have been found in any of the tests so far, check the vacuum system for leaks.