Air Flow Meter/Sensor: Testing and Inspection
Mass Air Flow (MAF) Sensor -G70-, Checking
Recommended special tools and equipment
- V.A.G 1526A multimeter
- V.A.G 1594A connector test kit
- V.A.G 1598/31 test box
Test requirements:
- Fuse for Mass Air Flow (MAF) sensor -G70- OK
- Ground (GND) connections at engine and transmission OK
- Fuel Pump (FP) Relay OK; checking. Fuel Pump (FP) Relay -J17- and Activation, Checking
- Parking brake engaged.
- Selector lever of automatic transmission 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 see"Mode 1: Check measuring values "; "PID 05: Coolant temperature". Mode 1: Check Measured Values
- Ignition switched off.
NOTE:
- Voltage is supplied to Mass Air Flow (MAF) sensor -G70- from Fuel Pump (FP) relay.
- Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) sensor -G70-.
Checking function
- Connect diagnostic tester. [1][2]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 -G70-".
- Specified value: 3.5 to 7.0 g/s
- End diagnosis and switch ignition off.
If the specified value is not reached:
- Check intake air system for leaks (false air). Intake System For Leaks (False Air), Checking
- Check voltage supply and wire connections
If the specified value is exceeded:
- Eliminate engine load via additional equipment (A/C system/power-assisted steering/generator).
- Check voltage supply and wire connections
Checking voltage supply
- Disconnect electrical harness connector -4- at Mass Air Flow (MAF) Sensor -G70-.
NOTE:
- Depicted in illustration with air filter cover removed.
- Disregard the other items as well as the arrow.
- Connect multimeter for voltage measurement as follows.
Harness connector Terminal Measure to
2 Engine Ground (GND)
- Operate starter briefly (engine can also start).
- 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.
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 and Component Test
- Check the following wire connections for open circuit according to wiring diagram:
Harness connector Terminal Measure to
3 27
4 53
5 29
Specified value: Wire resistance max 1.5 Ohms
- Check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinite Ohms (no continuity)
- If necessary, repair wire connection.
If no malfunctions are detected:
- Replace Mass Air Flow (MAF) Sensor -G70-
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". Mode 3: Check DTC Memory
2. If necessary, erase DTC memory see "Mode 4: Reset/erase diagnostic data". Mode 4: Reset/Erase Diagnostic Data
3. Generate readiness code. Readiness Code, Generating
- End diagnosis and switch ignition off.