Air Flow Meter/Sensor: Testing and Inspection

NOTE:
^ For functional testing of the Mass Air Flow sensor, also see On-Board Diagnostics, "Basic Setting" function 04. Testing and Inspection

TEST CONDITION
^ Circuit breaker in yellow fuse holder - OK (In electronics box, passenger side footwell)

CHECKING POSITIVE BATTERY VOLTAGE (B+) SUPPLY.
- Ignition switched OFF
- Disconnect harness connector from Mass Air Flow (MAF) sensor.

CAUTION:
Wait 30 seconds after switching OFF the ignition BEFORE disconnecting the Engine Control Module (ECM) harness connector.

- Connect multimeter (Fluke 83 or equivalent) between connector terminals 2 and 3 using adapter cables from VW 1594 connector test kit.
- Switch ignition ON.
Specified value: approx. 12-14 volts.

If specified value is not obtained:
- Check Circuit breaker in yellow fuse holder (In electronics box, passenger side footwell).
- Check continuity between connector terminal 3 and circuit breaker according to wiring diagram.
Specified value: maximum 0.5 ohms
- Check continuity between terminal 2 and Ground (GND).
Specified value: maximum 0.5 ohms

Check wiring between ECM and MAF sensor
- Connect VAG 1598 test box with VAG 1598/11 adapter harness to engine wiring harness. Refer to VAG 1598 Pin Out Box Connecting. Connecting VAG 1598/31 Test Box
Adapter harness for ECM is not connected.
- Check signal wire for continuity between MAF sensor terminal 1 and test box socket 42.
Specified value: maximum 1.0 ohm
- Check ground wire for continuity between MAF sensor connector terminal 2 and test box socket 45.
Specified value: maximum 1.0 ohm

If specified values are not obtained:
- Find and eliminate open or short circuit in wiring between MAF sensor connector and ECM connector A.

MAF sensor ECM connector A
connector
1 2
2 5

NOTE:
Use only gold-plated terminals when replacing mass air flow sensor connector terminals.

Checking function of MAF sensor
- Push back protective boot on MAF sensor connector (leaving sensor connected).

NOTE:
The connector terminals are appropriately identified on the back of the connector:

- Connect multimeter (Fluke 83 or equivalent) between connector terminals 1 and 2, using adapter cables from VW 1594 connector test kit.
- Switch ignition ON.
Specified value: 0.3-1.1 volts
- Let engine run, switch all electrical consumers off (radiator cooling fan must not run) and vary engine speed continuously between idle and 4000 RPM.
Specified value: voltage must vary between 1.5 to maximum 3.4 volts, corresponding to engine speed.

If specified values are not obtained:
- Replace mass air flow sensor.