1997 AUDI A4 check engine

24-155

Intake Manifold Tuning (IMT) function,
checking


Note:
The following test should only be conducted if
performance deficiencies occur.

- Increase engine rpm clearly above 4500 RPM.

Intake manifold tuning vacuum solenoid must be
actuated (solenoid is located on intake manifold,
left-front, under the ignition coils).
If the vacuum solenoid is not actuated:

- Check intake manifold tuning valve -N156-
(change-over valve) page 24
-156
.

- Check vacuum system for leaks page 24
-
162
.

- Check that vacuum lines are correctly installed,
do not leak and are not blocked.

- Check change-over mechanism for ease of
movement (activate change-over linkage by
hand).
Pa
ge 3 of 11 Intake Manifold Tunin
g (IMT
) syste
m
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.3

24-158

Checking voltage supply for intake manifold
tuning valve -N156-

Test requirements

Fuse for for intake manifold tuning valve OK

- Disconnect harness connector from intake manifold tuning valve.

If LED does not light up: - Connect LED test lamp VAG1527 with wires from test kit VAG1594
between terminal 1 (B+) of 2-pin connector and engine Ground.
- Crank starter.
LED must light up.
- Check fuse for -N156-
Pa
ge 6 of 11 Intake Manifold Tunin
g (IMT
) syste
m
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.3

24-162

Vacuum system, checking for leaks


- Let engine run 2 to 3 minutes at idle (for vacuum
to build up).

- Switch ignition off.

- Remove 2-pin connector from intake manifold
tuning valve -N156- (change-over valve).

- Connect jumper wire (from VAG1594) from one terminal of -N156- to
engine ground.
- Use VAG1248/3A remote, adapter wire VAG1348/3-2 and auxiliary
wire to connect second terminal of -N156- to B+.
- Activate intake manifold tuning valve -N156-, using remote control
VAG1348/3A, for approx. 2 to 3 min.
The vacuum solenoid must remain actuated during this time.
Pa
ge 10 of 11 Intake Manifold Tunin
g (IMT
) syste
m
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.3