Air Flow Meter/Sensor: Testing and Inspection

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.

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.

CHECKING SIGNAL WIRE:



- Connect VAG 1598/19 test box to ECM harness connector.
- Check signal wire for continuity between MAF sensor connector terminal 1 and test box socket A12.

Specified Value: max.1.0 Ohms.

If the specified value is not obtained:



- Find short circuit or open circuit; repair as necessary.

TERMINAL ASSIGNMENTS:
MAF Sensor ECM Connector A
1 A12

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.

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 max. depending on engine speed (RPM).

If the specified value is not obtained:
- Replace Mass Air Flow (MAF) sensor.