Air Flow Meter/Sensor: Testing and Inspection
Checking Mass Air Flow Sensor^ For functional testing of the mass air flow sensor, also see On-Board Diagnostics With Scan Tool VAG 1551, "Basic Setting" function 04. 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 and Testing VAG 1598 Pin Out Box
Adapter harness for ECM is not connected.
- Check signal wire (air flow signal) for continuity between MAF sensor terminal 1 and test box socket 42.
Specified value: maximum 1 (ohm)
- Check signal wire (CO% potentiometer) for continuity between MAF sensor connector terminal 4 and test box socket 41.
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
4 1
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 4, using adapter cables from VW 1594 connector test kit.
- Switch ignition on.
Specified value: 1.0-7.5 volts
If specified values are not obtained:
The CO% potetiometer is faulty. Replace mass air flow sensor.
- 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.