Air Flow Meter/Sensor: Testing and Inspection
Mass Air Flow (MAF) sensor -G70-, checking
Test conditions
- Coolant temperature at least 80 degrees C.
- Electrical consumers switched off (radiator fan must not run during the check)
- Air conditioner switched off
- Fuse for MAF sensor OK
Checking function
- Connect Vehicle Diagnostic, Testing and Information System VAS 5051 or V.A.G 1551 Scan Tool and select engine electronics control module 1 with "Address word" 01. For this purpose, engine must be running at idle speed.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press keys 0 and 4 for function "Introduction of basic setting" and confirm entry with Q key.
NOTE: During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve -N80- is closed and the air conditioning compressor is switched off by the engine control module.
Indicated on display
Basic setting Q
Enter display group number XXX
- Press keys 0, 0 and 2 for "display group number 2" and confirm entry with Q key.
Indicated on display
System in basic setting 2 ->
1 2 3 4
- Check specified results for recorded load.
Display Group 2:
If specified value is attained:
- Press ->key.
- Press keys 0 and 6 for "End output" function and press Q key to confirm entry.
- Switch ignition off.
Evaluation of display group 002
Display Zone 3:
Display Zone 4:
Checking voltage supply to MAF sensor
- Disconnect connector from MAF sensor.
- Connect hand-held multimeter for voltage measuring to socket 2 of connector and engine Ground.
- Operate starter briefly.
Specified value: approx. battery voltage
NOTE: Voltage supply to MAF sensor is from fuel pump relay. If battery voltage is not present:
If battery voltage is not present:
- Test wiring from socket 2 on connector via fuse to fuel pump relay for open circuit or short to Ground. Correct, if necessary.
If the specified value is achieved:
- Check Ground supply to engine control module.
Checking Ground connection
- Connect hand-held multimeter for voltage measuring to sockets 2 and 3 of connector.
- Operate starter briefly.
Specified value: approx. battery voltage
NOTE: Engine control module Ground is present at socket 3 of the connector.
If specified value is not attained:
- Check wiring connections.
- Connect hand-held multimeter for voltage measuring to sockets 3 and 4 of connector.
- Switch ignition on.
Specified value: approx. 5 V.
If specified value is not attained:
- Check wiring connections.
Checking wiring to MAF sensor
NOTE: The signal wire is also checked during the wiring check.
- Connect test box VAG 1598/31 to wiring harness for engine control module; engine control module must not be connected. Connecting VAG 1598/31 Test Box
- Check for open circuit and short to positive or Ground in following wiring connections:
Connector for MAF sensor
-G70-, socket Test box V.A.G 1598/31 socket
3 27
4 53
5(signal wire) 29
Wire resistance: max. 1.5 Ohm
- Correct any open/short circuit as necessary.
- Check all wires for short to one another.
Connector for MAF sensor
-G70-, socket Test box VAG 1598/31 socket
3 53 and 29
4 27 and 29
5 (signal wire) 27 and 53
Specified value: infinite resistance (open circuit)
- If voltage supply and wiring are OK, replace MAF sensor -G70-.
- Read readiness code. If DTC memory was erased, re-generate readiness code. Readiness Code, Generating