Air Flow Meter/Sensor: Testing and Inspection

Mass Air Flow sensor, checking

Special tools, testers, measuring instruments and auxiliary items required

- VAG 1551/1552 Scan Tool with VAG 1551/3B adaptor cable
- VAG 1598/22 Test Box
- Fluke 83 Multimeter
- VW 1594 Adaptor kit
- Wiring diagram

Check conditions

- Fuse 29 OK.






- Engine Coolant Temperature must be at least 85 °C, = Display group 04, Display zone 3
- All electrical consumers, e.g. lights and rear window defroster must be switched OFF
- A/C switched OFF (if installed).
- Transmission Range selector lever in "P" or "N" position (automatic transmission only)

Test sequence

- Connect VAG 1551/1552 Scan Tool, [1][2][3]Reading and Clearing Diagnostic Trouble Codes
- Start engine and let idle
- Press 0 and 1 buttons to select "Address word" 01 "Engine electronics"

Display will appear as shown

Rapid data transfer HELP
Select function XX

- Press 0 and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to enter input

Display will appear as shown

Read measuring value block HELP
Input Display group number XXX

- Press 0, 0 and 2 buttons to select "Display group 2"
- Press Q button to enter input

Display will appear as shown (1 to 4 = Display zones)

Read measuring value block 2 ->
1 2 3 4


- Check the load registration specifications (Display zones 2 and 4 on chart)







- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.

If the specifications are not obtained or there is a DTC stored in DTC memory related to the Mass Air Flow sensor:

- Check Mass Air Flow sensor Voltage supply as follows:

Voltage supply, checking

- Disconnect 4-pin harness connector -1- from Mass Air Flow sensor -2-.






- Switch Multimeter to Voltage range
- Connect Multimeter between connector terminals 1 and 3.
- Start engine and let idle.
- Specification: 11 to 15 Volts
- Switch OFF ignition.

If Voltage supply OK

- Test signal and Ground wires.

If NO Voltage present:

- Check wiring between terminal 3 to fuel pump relay J17 using Wiring diagram.

Signal wire, checking

- Connect VAG 1598/22 Test Box to ECM wiring harness.






- Check wiring for open circuit between Test Box and 4-pin harness connector using Wiring diagram.

Terminal 4 + socket 13
Terminal 2 + socket 12

Wire resistance: Max. 1.5 Ohms

- Check wiring for open circuit between 4-pin harness connector and Ground using Wiring diagram.

Terminal 1 + Ground

Wire resistance: Max. 1.5 Ohms

- Remove fuse 28.






- Check all wires for shorting to one another.

Specification: Infinity Ohms


NOTE: If fuse 28 is not removed the fuel pump will short circuit between connector terminals 1 + 3.

If wiring OK

- Replace Mass Air Flow sensor G70.

Evaluating Display group 2