Testing intake manifold flap change-over function: Audi 1.9 TDI (AJM, ATJ)

ATJ
Special tools and workshop equipment required

V.A.G 1390
V.A.G 1526 A
V.A.G 1527 B
V.A.G 1594 A
V.A.G 1598/31

Checking function

Start engine and run at idling speed.
Switch off ignition.
Observe positioning lever on intake manifold flap (2nd person required).
After switching off the ignition, the intake manifold flap should close and open again after approx. 3 seconds.

If change-over does not occur, the following checks must be carried out.

Check intake manifold flap change-over mechanics for freedom of movement. To do this operate rods by hand.
Check function of vacuum positioning element with hand vacuum pump V.A.G 1390.
Check vacuum pipes for correct connection.

If no fault is found in the mechanical components:

Unclip protecting covers.
Unscrew bolts -arrows- and remove air cleaner cover.
Unplug connector on intake manifold flap change-over valve -N239.

Testing internal resistance

Connect multimeter to valve (resistance measurement range)
Specification: 25 ... 45 ω

If the specification is not obtained:

Renew intake manifold flap change-over valve.

Checking voltage supply

Test requirement:

Fuse for intake manifold flap change-over valve OK

Connect multimeter (voltage measurement range) as follows:

Connector / Contact · Measure against
1 · Engine earth

Switch on ignition.
Specification: approx. battery voltage

If the specification is not obtained:

Test wiring for open circuits and rectify if necessary.

Checking activation

Connect voltage tester V.A.G 1527 B between contacts 1 and 2
Start final control diagnosis and select intake manifold flap change-over valve -N239 =>Page 01-55.
The LED should flash slowly.

Note:

The LEDs on voltage testers with a low current draw continue to glow faintly between impulses from the engine control unit (rather than going out completely) and become much brighter when receiving an impulse.

Finish off final control diagnosis.
Select diagnosis function "06 - End output" Page 01-11.
Switch off ignition.

If the LED does not react as described:

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 23-37.

Test for open circuit and short to positive or earth in the following wiring connections:

Connector / Contact · Test box V.A.G 1598/31 / Socket
2 · 81

Rectify any open/short circuit as necessary.

If no fault is found:

Fit a new engine control unit => Page 23-40.