Mass Air Flow (MAF) Sensor, Checking

Mass Air Flow (MAF) Sensor, Checking

NOTE: When servicing terminals in the harness connector for the Mass Air Flow (MAF) sensor or Intake Air Temperature (IAT) sensor, use only gold-plated terminals.

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

Test requirements







- Corresponding fuses on fuse holder in instrument panel, left side, for Mass Air Flow (MAF) Sensor -G70- must be OK.

NOTE: Fuses on this fuse holder are labelled "SC" in the wiring diagram.

- Battery voltage must be at least 11.5 Volts.
- All electrical consumers such as, for example, lights and rear window defroster must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- Steering wheel stands in center position.
- For vehicles with automatic transmission, selector lever must be in -P-.
- Air filter not blocked or soiled.
- Vacuum actuator for intake manifold flaps must be OK, checking.
- Intake air pre-heating must be OK, checking.
- No leaks in intake system, checking intake air system for leaks (false air).
- Coolant temperature must be at least 80 degrees C, Diagnostic mode 1: Check measured values; PID 5 ($5), Coolant temperature.
- Ignition switched off.

Function test
Observe safety precautions.
Observe rules for cleanliness.

- Connect diagnostic tester.
- Start engine and let run at idle.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select the measuring value "PID 16 ($10): 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.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If specified value is not obtained:
- Check wires to Engine Control Module (ECM) according to wiring diagram.

Checking voltage supply







- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor -G70-.







- Connect multimeter using adapter cables to terminal 5 of connector and engine Ground (GND) for voltage measurement.
- Start engine, and let run at idle.

Specified value: at least 11.5 V

- Switch ignition off.

If there is a malfunction in voltage supply:
- Check wire between 5-pin connector terminal 5 and fuse holder for open circuit according to wiring diagram.

Wire resistance: max. 3.0 ohms

If there is no malfunction in voltage supply:
- Check wires to Engine Control Module (ECM) according to wiring diagram.

Checking wires to Engine Control Module (ECM)







- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor -G70-.
- Connect test box to 94-pin connector of wiring harness, connecting test box for wiring test.

Engine Control Module (ECM) is not connected.







- Check wires between test box and 5-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 1 + socket 22
Terminal 2 + socket 42
Terminal 4 + socket 64

Wire resistance: max. 3.0 ohms

- Also check wires for short circuit to each other.

Specified value: infinity ohms

- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If no malfunctions are found in wires:
- Replace Mass Air Flow (MAF) Sensor -G70- with Intake Air Temperature (IAT) Sensor - G42-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes