Vacuum System, Checking

Vacuum System, Checking

Special tools, testers and auxiliary items required

• (VAG1348/3-2)

• (VAG1348/3A)

• (VAG1390)

• (VAG1594A)

Test sequence

- Run engine at idling speed for 2 or 3 minutes to build up vacuum pressure.

- Switch ignition off.

- Remove front engine cover (arrows).





- Disconnect connectors to intake manifold change-over valve (N156) - 1 -.





- Connect one terminal on solenoid valve to engine Ground using test leads and alligator clamp from (VAG1594A).





- Connect second terminal on intake manifold change-over valve (N156) to positive using remote control (VAG1348/3A), adapter lead (VAG1348/3-2 ) and auxiliary cable.

- Operate remote control (VAG1348/3A) approx. 2 to 3 minutes; throughout this period, vacuum module should remain energized.

If the vacuum module retardations to its original "rest" position, perform the following test:

- Disconnect vacuum hoses from vacuum module for intake manifold change-over system.

- Connect hand vacuum pump (VAG1390) to vacuum module.

- Operate hand pump and check whether change-over function is working.

- Check vacuum module for leaks. (Vacuum module should not return to rest position until hand pump is vented to atmosphere.)

- Replace vacuum module, if necessary.

- If vacuum module is not energized, check intake manifold changeover valve (N156) as follows for blockage:

- Connect one terminal of intake manifold change-over valve (N156) to engine Ground using test leads and alligator clamp from (VAG1594A).





- Connect second terminal on intake manifold change-over valve (N156) to positive using remote control (VAG1348/3A), adapter lead (VAG1348/3-2 ) and auxiliary cable.

- Operate remote control (VAG1348/3A).

- Check valve for obstructions (disconnect vacuum hoses and blow through).

- Replace intake manifold change-over valve, if necessary.

- If no DTCs have been found in any test, check vacuum system for leaks.