Air Flow Meter/Sensor: Testing and Inspection

Mass Air Flow (MAF) Sensor, Checking

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

Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram

Requirements







- The respective fuse of Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42- must be OK:
- Fuel Pump (FP) relay -J17- must be OK, check:
- Battery voltage must be at least 11.5Volts.
- All electrical consumers such as, lights and rear window defroster must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in position -P- or -N-.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- Coolant temperature must be at least 80 degrees C, Diagnostic mode 1: Check measured values; PID 5, Coolant temperature. Diagnostic Mode 1: Check Measured Values

Function test
- Connect diagnostic tester. Diagnostic Tester, Connecting
- Start engine and let run at idle.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select the measuring value "PID 16: Air flow 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 obtained, but DTC memory has a DTC concerning Mass Air Flow (MAF) sensor:
- Check voltage supply of Mass Air Flow (MAF) sensor.

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

Voltage supply for Mass Air Flow (MAF) sensor, checking







- Disconnect 5-pin connector from Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42- (arrow).







- Connect multimeter to terminal 2 of connector and engine Ground (GND) for voltage measurement.
- Start engine, and let run at idle.

Specified value: 11.0 to 15.0 V

- Switch ignition off.

If there is no voltage:
- Check wire between 5-pin connector terminal 2 and the Fuel Pump (FP) relay -J17- for open circuit according to wiring diagram.

Wire resistance: max. 1.5 Ohms

If voltage supply and wires are OK:







- Connect multimeter to terminal 4 of connector and engine Ground (GND) for voltage measurement.
- Switch ignition on.

Specified value: at least 4.5 V

- Switch ignition off.

If there is no voltage:
- Check signal and Ground (GND) wire of Mass Air Flow (MAF) sensor.

Checking signal and Ground wires of Mass Air Flow (MAF) sensor
- Connect test box to control module wiring harness, connect test box for wiring test.

Vehicles with engine code AEG







- Check wires between test box and 5-pin connector for open circuit according to wiring diagram.

Terminal 3 + socket 12
Terminal 4 + socket 11
Terminal 5 + socket 13

Wire resistance: max. 1.5 Ohms

Vehicles with engine code AVH, AZG, BBW, BEV







- Check wires between test box and 5-pin connector for open circuit according to wiring diagram.

Terminal 3 + socket 27
Terminal 4 + socket 53
Terminal 5 + socket 29

Wire resistance: max. 1.5 Ohms

Continued for all vehicles
- Check wires for short circuit to each other, to vehicle Ground (GND) and to B+.

Specified value: Infinite Ohms

If no DTCs are found in wires:
- Replace Mass Air Flow (MAF) sensor -G70-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes