Air Flow Meter/Sensor: Testing and Inspection

Checking Mass Air Flow Sensor

Notes:
^ Starting with ECM 8A0 906 266 B, an oxygen sensor control with adaptive learning is used, which means that the CO fuel trim potentiometer on the mass air flow sensor is eliminated.

^ For functional testing of the mass air flow sensor, also see "Basic Setting" function 04, display group 001, display field 2 and/or 3. Basic Setting (Function 04)

Test condition.

^ MAF sensor circuit breaker (S74) - OK (black holder in electronics box, passenger side footwell)

Checking positive battery voltage (B+) supply.

- Ignition switched OFF

- Disconnect harness connector from 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 MAF sensor circuit breaker (S74) (black 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 (ohm)

- Check ground wire for continuity between MAF sensor connector terminal 2 and test box socket 45.
Specified value: maximum 1 (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 2 and 1, 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.