Mass Air Flow (MAF) Sensor, Checking

Mass Air Flow (MAF) Sensor, Checking

The MAF sensor is located in the upper air cleaner housing.

Checking function
- Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). [1][2]Scan Tool Connecting and Initial Checks

Indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display


Read Measuring Value Block
Input display group number XXX


- Press buttons -0-, -0- and -7- to input display group number 7 (007), and press -Q- button to confirm input.

Indicated on display


Read Measuring Value Block 7 ->
1 2 3 4


- Check specified values for mass air flow sensor (display fields 1 and 2):







If the displayed values are not OK:
- Check intake air system for intake air system for leaks ("false air").

If there are no leaks:
- Check MAF sensor voltage supply.
- Press -> button to advance program sequence.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

Checking MAF sensor -G70-
- Check fuse for MAF sensor (E-box in plenum).

If fuse is OK:
- Remove upper air cleaner housing.
- Disconnect MAF sensor harness connector.







- Connect VAG1527B LED voltage tester between harness connector terminal 3 and engine Ground.
- Briefly operate starter (engine can start briefly).
LED must light up.







If LED does not light:
- Check wiring for open circuit or short to Ground between connector terminal 3 and fuse.

If fuses and wiring are OK but LED still does not light:
- Check fuel pump relay. Refer "Fuel Pump", "Fuel Pump Relay" Testing and Inspection

If voltage supply is OK:
- Connect VAG1598/19 test box to ECM harness connector. Connecting VAG 1598/19 Test Box






- Check wiring for open or short circuits between MAF sensor connector terminal 1 (Ground) and ECM/test box socket E7.







- If necessary, repair open circuit between connector terminal 1 and ECM terminal E7.

If voltage supply is OK:
- Check signal wiring.

Checking MAF sensor signal wiring
- Connect VAG1598/19 test box to ECM harness connector. Connecting VAG 1598/19 Test Box







- Check wiring and connections for open or short circuits as follows:

Mass Air Flow (MAF) sensor VAG1598/19 test box socket (ECM
-G70-connector terminal terminal)
2 B18
4 B19

If wiring and connections are OK:
- Check intake air system for leaks ("false air").

If there are no leaks:
- Replace MAF sensor.
- Check readiness code. If DTC memory has been erased, generate new readiness code.
Readiness Code Reading
Readiness Code, Generating