AUDI A4 1999 B5 / 1.G AFC Engine Mass Air Flow Sensors Checking Workshop Manual

24-81


Mass Air Flow (MAF) sensor,
checking

Notes:

To functionally check the Mass Air Flow (MAF)
sensor Repair Group 01, Basic setting,
display group 001, display field 2.

Component locations page 24
-1 .

Checking voltage supply

Mass Air Flow (MAF) sensor fuse OK

- Disconnect MAF sensor harness connector.

- Switch multimeter (Fluke 83 or equivalent) to measure voltage and
connect between connector terminals 2 (GND) and 3 (B+) using jumper
wires from connector test kit VW 1594.
- Switch ignition ON.
Specified value: approx. 12 to 14 volts
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If the specified value is not obtained, perform the
following tests:

- Check Mass Air Flow (MAF) sensor fuse.

- Check wiring for continuity between terminal 3
and fuse using wiring diagram.


Specified value: max. 0.5 ohms( )
- Check wiring for continuity between terminal 2
and intake manifold Ground (GND).


Specified value: max. 0.5
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Checking signal wire

If the specified value is not obtained: - Connect VAG 1598/19 test box to ECM harness connector page 01
-
255
.
- Check signal wire for continuity between MAF sensor connector
terminal 1 and test box socket A12.

Specified value: max.1.0

Note:
If it becomes necessary to repair or replace any of the Mass Air Flow
(MAF) sensor electrical terminals, ONLY replace with gold-plated
terminals. - Find short circuit or open circuit; repair as necessary.MAF sensor connector terminal
ECM connector A terminal
1 A12
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Checking function

- Slide back protective boot from back of MAF
sensor connector (leaving it connected).

Note:
The connector pin numbers are marked on the
back of the connector itself.

- Switch multimeter (Fluke 83 or equivalent) to
measure voltage and connect between terminal
2 (GND) and terminal 1 (B+) using jumper wires
from connector test kit VW 1594.

- Switch ignition ON.

Specified value: 0.3 to 1.1 volts

- Start engine and let idle.

- Switch off all electrical consumers (engine
coolant fan should not run during measurement).

Continuously vary engine speed between idle
and 4000 RPM.


Specified value: 1.5 volts minimum to 3.4 volts
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max. depending on engine speed (RPM)
If the specified value is not obtained:

- Replace Mass Air Flow (MAF) sensor.
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