check engine AUDI A4 1996 B5 / 1.G AFC Engine Intake Manifold Change Over Checking Workshop Manual

24-85


Intake manifold change-over,
checking
Carry out this check only if complaints of "vehicle
under-powered" are received.
Intake manifold change-over from the "long" to
"short" intake path occurs at approx. 4000 RPM.

Checking function

- Raise engine speed above 4000 RPM.

Vacuum canister for intake manifold change-
over valve (on intake manifold, left rear)
must tighten.
If canister does not tighten:

- Check intake manifold change-over valve using
output Diagnostic Test Mode page 01
-145
,.

If necessary check valve and triggering page
24
-64
.

- Check vacuum reservoir for leaks page 24
-
111
.

-
Check vacuum lines for correct routing, leakage
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24-86

Checking vacuum system

- Start engine and let idle for two to three minutes
to build up vacuum.

- Switch ignition OFF.

- Disconnect 2-pin harness connector from intake
manifold change-over valve.

If the vacuum canister returns to its original position, check as follows: - Using jumper wires from connector test kit VW 1594:
- Connect either connector terminal to intake manifold Ground (GND)
point.
- Connect remaining terminal to VAG1348/3A remote control.
- Connect VAG1348/3-2 adapter wire to B+.
- Activate remote for approx. 2 to 3 minutes, during which time vacuum
canister must remain connected.
- Switch ignition OFF.
- Disconnect vacuum lines from intake manifold change-over vacuum
canister.
- Connect US 8026 hand pump to vacuum canister.
- Operate hand pump and note change-over operation.
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