Air Flow Meter/Sensor: Testing and Inspection

Mass Air Flow (MAF) Sensor -G70-, Checking







Special tools and equipment
- VAG1526 A
- VAG1594 A
- VAG1598/31
- VAS5051 with VAS5051/1

Test requirements:
- Engine coolant temperature at least 80 degrees 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 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 square 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.

NOTE: 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.

Connector Measure to
terminal
2 Engine ground

- 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

NOTE: 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

NOTE: 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.







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

Connector Test box VAG1598/31
terminal Socket
1 53
3 27
4 29

- 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-.