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

Mass Air Flow (MAF) Sensor - G70, Checking

Requirements
- Coolant temperature at least 80 °C (175 °F)
- Electrical consumers switched off (radiator fan must not run during test)
- A/C switched off
- Fuse for mass air flow sensor OK

Checking function
- Connect vehicle diagnostic, testing and information system VAS5051 or VAG1551 scan tool and select engine electronics control module by entering address word "01. When doing this the engine must be at idle. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/" Testing and Inspection

Indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -4- to select function "Basic Setting" and confirm entry with -Q- button.


NOTE: During the basic setting the engine control module closes the EVAP canister purge regulator valve -N80 and switches off the A/C compressor.


Indicated on display


System in Basic Setting Q
Input display group number XXX


- Press buttons -0-, -0- and -2- to select Display Group 002 and confirm entry with -Q- button.

Indicated on display


System in basic setting 2 ->
1 2 3 4


- Check displayed specified values for engine load.

Read measuring value block display group 2 as described and evaluate it. If the suggested repair steps refer to the voltage supply test for the Mass Air Flow (MAF) sensor or the wiring connections from the Mass Air Flow (MAF) sensor to the Engine Control Module (ECM), proceed to the following pages.

Please note the distinction between sensors made by Bosch and those made by Hitachi (recognizable via the writing on the sensor).

Checking voltage supply to Mass Air Flow (MAF) sensor
- Disconnect harness connector from air mass meter.







- Connect hand-held multimeter (voltage measurement range) between engine Ground (GND) and socket 2 of connector.
- Operate starter briefly.

Specification: approx. battery voltage


NOTE: The mass air flow sensor receives its voltage supply via the fuel pump relay.


If the reading does not match the battery voltage:
- Check for open circuit or short to Ground (GND) in wiring between fuel pump relay and socket 2 on connector via fuse. Repair if necessary.
- Connect hand-held multimeter (voltage measurement range) between sockets 2 and 3 of connector.
- Operate starter briefly.
Specification: approx. battery voltage


NOTE: Socket 3 on the connector is the Ground (GND) connection from the engine control module.


If the specification is not attained:

- Check wiring.
- Connect hand-held multimeter (voltage measurement range) between sockets 3 and 4 of connector.
- Switch ignition on.
Specification: approx. 5 V

If the specification is not attained:
- Check wiring.

Checking wiring for mass air flow sensor


NOTE: The wiring test includes also testing the signal wire.


- Connect VAG1598/31 test box to wiring harness for engine control module. Do not connect to the engine control module itself. Refer to "Scan Tool Testing/Wiring And Component Check With VAG1598/31 Test Box", Testing and Inspection
- Check for open circuit and short to B+ or Ground (GND) in the following wiring connections:







Connector for VAG1598/31
Mass Air Flow test box terminal
(MAF) sensor -G70
3 27
4 53
5 29

Resistance in wiring: max. 1.5 Ohms
- Repair short circuit or open circuit if necessary.

Specification: Infinity Ohms (open circuit)
- If wiring and voltage supply are OK, replace Mass Air Flow (MAF) sensor -G70.