AUDI A4 1995 B5 / 1.G AFC Engine Idle Air Control Valve Checking Workshop Manual

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Idle Air Control (IAC) valve,
checking

Note:
To functionally check the idle speed control
system "Read Measuring Value Block"
function 08, display groups 004 through 018.
Electrical checks

- Disconnect Idle Air Control (IAC) valve harness connector.

If the specified resistance is not obtained: - Measure IAC valve resistance by connecting multimeter (Fluke 83 or
equivalent) between connector terminals using jumper wires from
connector test kit VW 1594.

Specified value: 7 to 11 - Replace Idle Air Control (IAC) valve.
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Note:
At room temperature, the resistance value will be lower. The resistance
value will be higher if the Idle Air Control (IAC) valve is measured at
under-hood operating temperatures.
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Checking mechanical function

- Remove Idle Air Control (IAC) valve.

CAUTION!
Do not check for ease of movement by prying on the rotary slide
using a screwdriver or other tools that could potentially cause
scratching.
If there are signs of scoring that impair free movement, or if the rotary
slide does not move freely (sticks, moves slowly or does not move fully in
both directions):
If the valve does not react (not triggered) during the output Diagnostic
Test Mode: - Visually check surface of rotary slide (arrow) for signs of wear.
- Re-connect valve (still removed) to harness connector.
- Switch ignition ON.
- Use scan tool "Output Diagnostic Test Mode" function 03 to trigger Idle
Air Control (IAC) valve -N71- Repair Group 01. - Check whether rotary slide moves smoothly and freely from stop to
stop.
- Replace Idle Air Control (IAC) valve.
- Check triggering.
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Checking Idle Air Control (IAC) valve
triggering

Idle Air Control (IAC) valve electrically OK

- Slide up boot on Idle Air Control (IAC) valve
connector.

- Use scan tool "Output Diagnostic Test Mode"
function 03 to trigger Idle Air Control (IAC) valve
-N71- Repair Group 01.

If specified results are not obtained: - Connect VAG 1527B voltage tester between connector terminal 1 and
engine Ground (GND).
Specified result: voltage tester must flash
- Connect voltage tester between connector terminal 2 and battery
positive voltage (B+).
Specified result: voltage tester must light up
- Connect VAG 1598/19 test box to ECM harness connector (ECM is left
disconnected) Repair Group 01.
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If the wiring is OK but triggering still does NOT occur:
If the triggering signal and the wiring are OK and the valve still does not
react: - Check wiring between harness connector terminal 1 (in engine
compartment) to test box socket D11, then check wiring between
harness connector terminal 2 and test box socket D9 using wiring
diagram; correct as necessary.
- Replace ECM Repair Group 01.- Replace Idle Air Control (IAC) valve.
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