Mass Air Flow Sensor, Checking

Mass Air Flow Sensor, Checking

NOTE: Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) Sensor.

Recommended Special Tools, Workshop Equipment, Testers, Measuring Instruments and Auxiliary Items
- V.A.G 1526 portable multimeter or V.A.G 1715 multimeter
- Adapter set V.A.G 1594
- Wiring diagram

Test Conditions
- The corresponding fuses of Mass Air Flow (MAF) Sensor -G70- must be OK
- Fuel Pump (FP) Relay -J17- must be OK, check
- Battery voltage must be at least 11.5 V.
- All electrical consumers such as, for example, lights and rear window defroster must be switched off.
- The parking brake must be applied, otherwise the daytime running lights are switched on.
- If the vehicle is equipped with an air conditioning system, this must be switched off.
- The Ground (GND) connections between engine and body must be OK.
- Coolant temperature must be at least 80 degrees C: Diagnostic Mode 01 - Read Current System Data Check measured values; PID 5, Coolant temperature.

Function Test
- Connect diagnostic tester. Diagnostic Tester, Connecting
- Start engine and let run at idle.
- Under address word 33, select "Diagnostic mode 1: Checking measuring values."
- Select the measuring value "PID 16: Airflow quantity at Mass Air Flow (MAF) sensor".
- Check specified value of air flow quantity at Mass Air Flow (MAF) Sensor at idle:







- End diagnosis and switch ignition off.

If specified value is attained, but DTC memory has a DTC concerning Mass Air Flow (MAF) Sensor:
- Check Mass Air Flow (MAF) sensor voltage supply.

If the specification is not obtained:
- Check Mass Air Flow (MAF) sensor signal and Ground (GND) wires.

Mass Air Flow Sensor Voltage Supply, Checking
- Disconnect Mass Air Flow (MAF) Sensor connector.







- Connect multimeter to terminal 2 of connector and engine Ground (GND) for voltage measurement.
- Briefly operate starter.
Specification: approx. battery voltage

If no voltage is present:
- Switch off ignition.
- Check wiring harness from terminal 2 to Fuel Pump (FP) Relay -J17- according to wiring diagram.

If voltage supply and wiring are OK:
- Switch ignition on.
- Connect multimeter to terminal 4 of connector and engine Ground (GND) for voltage measurement:







Specification: 4.5 to 5.5 V

If no voltage is present:
- Switch off ignition.
- Check signal and Ground (GND) wires.

Signal and Ground Wires of Mass Air Flow Sensor, Checking
- Connect test box to control module wiring harness. Test Box, Connecting For Wiring Test

The Engine Control Module (ECM) remains disconnected.
- Check wires between test box and 5-pin connector for open circuit according to wiring diagram.

Terminal 5 + Socket 29

Terminal 4 + Socket 53

Terminal 3 + Socket 27







Wiring resistance: max. 1.5 Ohms

- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.

Specification: Infinity Ohms

If no fault is detected in the wiring:
- Replace Mass Air Flow (MAF) Sensor G70.
- Erase DTC memory of ECM. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Generate Readiness Code