With Generic Scan Tool

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
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test requirements






- The respective 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 volts.
- All electrical consumers like, for example, lights and rear window heating 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 degree C, Diagnostic mode 1: Check measuring 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: Checking 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. Specified value: 2.00 to 5.00 g/sec
- 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. Test Box, Connecting 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






- 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

Continuation for all vehicles
- Also 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-, item no. 3.
- 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