Manufacturer's Scan Tool

Mass Air Flow Sensor, Checking

Special tools, testers and auxiliary items required

• Multimeter (V.A.G 1526 A)

• Connector test kit (V.A.G 1594 A)

• Test Box (VAG1598/31)

• Vehicle diagnostic, testing and information system ( VAS 5051)

• Adapter (VAS 5051/1)

Component location. Refer to => [ Component Locations, Overview ] Locations.

Requirements

• Coolant temperature at least 80 °C.

• Electrical consumers switched off (coolant fan must not run during the test).

• Air conditioning switched off.

Checking function

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

Display on (VAS 5051):





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

Display on (VAS 5051):





1. Enter display group

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

Display on (VAS 5051):





- Activate basic setting by pressing A button.

- Check indication in display fields - 3 - and - 4 -.





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

Evaluation of display group 002





Voltage supply to Mass Air Flow (MAF) sensor (G70), testing

Requirements

• Fuse for Mass Air Flow (MAF) sensor OK.

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

• Voltage supply to Mass Air Flow (MAF) sensor is from Fuel Pump (FP) Relay (J17).

- Disconnect connector (arrow) to Mass Air Flow (MAF) sensor





- Connect multimeter as follows to measure voltage.









- Operate starter briefly.

• Specified value: approx. battery voltage (B+)

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 hand-held multimeter to terminals 2 and 3 of connector to measure voltage.





- Operate starter briefly (engine may start).

• Specified value: approx. battery voltage (B+)

• Engine control module ground (GND) is present at terminal 3 of the connector.

If specified value is not obtained:

- Check wiring

- Connect hand-held multimeter to terminals 3 and 4 of connector to measure voltage.





• Specified value: approx. 5 V

If specified value is not obtained:

- Check wiring.

Wiring to Mass Air Flow (MAF) sensor (G70), checking

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

- Connect test box (VAG1598/31) to wiring harness for ECM; do not connect ECM. Refer to => [ Electrical Testing, with Test Box VAG 1598/31 ] Electrical Testing, With Test Box VAG 1598/31.

- Check for open circuit, short to positive, or short to ground (GND) in following wiring connections:









- Repair any open/short circuit as necessary.

- Additionally check all wires for short to one another.

If the wiring is OK:

- Replace Mass Air Flow (MAF) sensor (G70).