With Generic Scan Tool

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

Recommended special tools and equipment







- VAG1526A hand multimeter
- VAG1594A connector test kit
- VAG1598/31 test box

Test requirements:
- Fuse for Mass Air Flow (MAF) sensor OK
- Ground (GND) connections at engine and transmission OK
- Fuel Pump (FP) Relay OK; checking. Testing and Inspection
- Parking brake engaged.
- Vehicles with automatic transmission: Selector lever in position "P" or "N".
- Electrical consumers switched off (radiator fan must NOT run during test).
- A/C switched off.
- Coolant temperature at least 80 degrees C "Mode 1: Check measuring values"; "PID 05: Coolant temperature".
- Ignition switched off.


NOTE:
- Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP) relay.
- Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) sensor.


Checking function
- Connect diagnostic tester.
- Start engine and let run at idle.
- In diagnostic function "33 - OBD", select "Mode 1: Checking measured values."
- Select the desired measuring value "PID 16: Air flow quantity at Mass Air Flow (MAF) sensor".
- Specified value: 2,0 ... 4.5 g/s

- End diagnosis and switch ignition off.

If the specified value is not reached:
- Check intake air system for leaks (false air) Testing and Inspection
- Check voltage supply and wire connections

If the specified value is exceeded:
- Eliminate engine load via additional equipment (A/C system/power-assisted steering/alternator).
- Check voltage supply and wire connections

Checking voltage supply







- Disconnect harness connector -arrow- at Mass Air Flow (MAF) sensor.







- Connect multimeter for voltage measurement as follows.

Harness connector Terminal Measure to
2 Engine Ground (GND)

- Operate starter briefly.
- Specified value: approx. battery voltage

- Switch ignition off.

If specified value is not obtained:
- Check wire connection from harness connector terminal 2 to Fuel Pump (FP) Relay -J17- via fuse for open circuit according to wiring diagram.
- Specified value: Wire resistance max 1.5 Ohm

- If necessary, repair wire connection.

If voltage supply is OK:

Check Ground (GND) activation







- Connect multimeter between terminal 2 and 3 of harness connector for voltage measurement.
- Operate starter briefly.
- Specified value: approx. battery voltage

If specified value is not obtained:
- Check wire connections







- Connect multimeter between terminal 3 and 4 of harness connector for voltage measurement.
- Switch ignition on.
- Specified value: about 5 V

- Switch ignition off.

If specified value is not obtained:

Checking wire connections


NOTE: Signal wire is also checked during wire test.


- Connect test box to wiring harness of Engine Control Module (ECM); ECM is not connected. Test Box, Connecting For Wiring Test







- Check the following wire connections for open circuit according to wiring diagram:

Harness connector Terminal Test box Socket
3 27
4 53
5 29

- Specified value: Wire resistance max 1.5 Ohm

- Also check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinite Ohm (no continuity)

- If necessary, repair wire connection.

If no malfunctions are detected:
- Replace Mass Air Flow (MAF) sensor -G70-, see -item 25-.

Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1 - Check DTC memory, see "Mode 3: Check DTC memory". Diagnostic Mode 3: Check DTC Memory
2 - If necessary, erase DTC memory, see "Mode 4: Reset/erase diagnostic data". Diagnostic Mode 4: Reset/Erase Diagnostic Data
3 - Generate readiness code Readiness Code, Generating

- End diagnosis and switch ignition off.