With Generic Scan Tool

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

Recommended special tools and equipment







- VAG1526A 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. With Generic Scan Tool
- 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 degree C "Mode 1: Check measuring values "; "PID 05: Coolant temperature". Diagnostic Mode 1: Check Measured Values
- 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. Diagnostic Tester, Connecting
- 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: 1.0 ... 5.0 g/s
- End diagnosis and switch ignition off.

If the specified value is not reached:
- Check intake air system for leaks (false air).
- 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







- Remove cover -1- in engine compartment (right side).







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







- Connect multimeter for voltage measurement as follows.

Harness connector Measure to
Terminal
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 Ohms
- 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
- Switch ignition off.
- Check wire connections.







- Connect multimeter between terminal 1 and 3 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 Testing







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

Harness connector Test box
Terminal Socket
1 53
3 27
4 29

- Specified value: Wire resistance max 1.5 Ohms
- Also check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinity Ohms (no continuity)
- If necessary, repair wire connection.

If no malfunctions are detected:
- Replace Mass Air Flow (MAF) sensor -G70- -item 2-.

Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1 - Check DTC memory "Mode 3: Check DTC memory". Diagnostic Mode 3: Check DTC Memory
2 - If necessary, erase DTC memory "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.