Manufacturer's Scan Tool

Mass Air Flow Sensor, Checking

Special tools, testers and auxiliary items required

• (VAG1526A)

• (VAG1594A)

• (VAG1598/31)

• (VAS5051) with (VAS5051/1)

Location overview. Refer to => [ Fuel Injection System Component Locations ] Locations.

Test requirements:

• Engine coolant temperature at least 80 °C.

• Electrical accessories switched off (radiator fan must not run during the test).

• Air conditioning switched off.

Checking function

- Connect testing and information system (VAS5051 ). Refer to => [ VAS 5051, Connecting and Select Functions ] VAS 5051, Connecting and Select Functions and select vehicle system "01 -Engine electronics" in selection. Engine must be running at idling speed.

Display on (VAS5051):





- Under - 1 - select diagnostic function "04 - Basic setting".

Display on (VAS5051):





1. Enter display group max. input value = 255

- Enter "002" for "display group number 002" in zone - 2 - and confirm entry by pressing Q button.

Display on (VAS5051):





- Activate basic setting by pressing - A - button.

- Check specifications for load recognition in display zones - 3 - and - 4 -.

All models





- Exit function "04 - Basic setting" by pressing arrow button.

Evaluation of display group 002





Testing voltage supply to mass air flow (MAF) sensor

Test requirements:

• Fuse for mass air flow (MAF) sensor OK.

• Fuel pump relay OK; checking. Refer to => [ Fuel Pump Relay and Activation, Checking ] Fuel Pump Relay and Activation, Checking.

• Voltage supply to mass air flow (MAF) sensor is from fuel pump relay.

- Disconnect cover - 1 - on right in engine compartment.





- Disconnect connector (arrow) to mass air flow (MAF) sensor.





- Connect multimeter as follows to measure voltage.









- Operate starter briefly.

• Specified value: approx. battery voltage

If specified value is not obtained:

- Check wiring from terminal 2 on connector via fuse to fuel pump relay for open circuit or short to Ground.

- Repair any open/short circuit as necessary.

If specified value is obtained:

- Connect multimeter between terminals 2 and 3 to measure voltage.





- Operate starter briefly (engine may start).

• Specified value: approx. battery voltage

• Engine control module Ground is present at terminal 3 of the connector.

If specified value is not obtained:

- Check wiring connections.

- Connect multimeter between terminals 1 and 3 to measure voltage.





• Specified value: approx. 5 V

If specified value is not obtained:

Checking wiring to mass air flow (MAF) sensor

• The signal wire is also checked during the wiring check.

- Connect test box (VAG1598/31) to wiring harness for engine control module; do not connect engine control module. Refer to => [ Wiring and Component Check with Test Box VAG 1598/31 ] Wiring and Component Check With Test Box VAG 1598/31.

- Check for open circuit and short to positive or Ground in following wiring connections:









- Repair any open/short circuit as necessary.

- Check all wires for short to one another.

If no wiring malfunction is detected:

- Replace mass air flow (MAF) sensor (G70).