With Manufacturer's Scan Tool
Mass Air Flow (MAF) sensor, checking
NOTE: Only gold plated contacts can be used to repair terminals in the connector for the Mass Air Flow (MAF) sensor.
Special tools and equipment
- VAG1551 Scan Tool (ST) or VAG1552 mobile scan tool with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter (Fluke 83 or equivalent)
- VW1594 adapter set
- Wiring diagram
Test requirements
- Fuse 43 OK
- Battery (B+) voltage at least 11.5 V
- Fuel pump relay OK
- All electrical consumers (e.g. lights and window defroster) must be switched off
- A/C switched off
- Automatic transmission selector lever in "P" or "N" position (if equipped)
- Coolant temperature at least 85 °C. See display group 04, display field 3.
Test sequence
- Connect VAG1551 (VAG1552) Scan Tool (ST).
- Switch ignition on and press buttons -0- and -1- to insert "Engine Electronics" address word 01. When doing this engine must be running at idle.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block
Input display group number XXX
- Press buttons -0-, -0- and -2- to input display group number 2 (002) and press -Q- button to confirm input.
Indicated on display (1-4 = display fields)
Read Measuring Value Block 2 ->
1 2 3 4
- Check air mass drawn in in display field 4.
Display Group 002:
- If value is as specified, DTC memory has recorded a malfunction relating to Mass Air Flow (MAF) sensor, test signal and Ground (GND) wires of Mass Air Flow (MAF) sensor.
If the specified value is obtained:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.
Evaluating display group 2, display field 4 - Air mass drawn in
Testing power supply to Mass Air Flow (MAF) sensor -G70-
- Disconnect 5-pin harness connector from Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42- (arrow).
- Connect multimeter to measure voltage on harness connector terminal -2- and engine Ground (GND).
- Start engine and run at idle.
Specified value: 11.0-15.0 V
If no voltage is present:
- Switch ignition off.
- Check wire between 5-pin harness connector terminal -2- and Fuel Pump (FP) relay -J17- for open circuit according to wiring diagram.
Wire resistance: max. 1.5 ohms
If the voltage supply and wiring is OK:
- Connect multimeter to measure voltage on harness connector terminal -4- and engine Ground (GND).
- Switch ignition on.
Specified value: min. 4.5 V
If no voltage is present:
- Switch ignition off.
- Check signal and Ground (GND) wires.
Testing signal and Ground (GND) wires for Mass Air Flow (MAF) sensor
- Remove wiper arms and plenum chamber cover.
- Connect VAG1598/31 test box to Engine Control Module (ECM) wiring harness. Engine Control Module (ECM) is not connected by this action.
- Check wiring between test box and 5-pin harness connector for open circuit according to wiring diagram.
- Terminal -5- + socket 29
- Terminal -4- + socket 53
- Terminal -3- + socket 27
Wire resistance: max. 1.5 ohms
- Additionally, check all wires for short circuit to one another.
Specified value: infinity ohms
- Check wiring additionally for short circuit to battery positive (B+)/Ground (GND).
If no malfunction is found in the wiring:
- Replace Mass Air Flow (MAF) sensor -G70- item 4. Refer under "Fuel Delivery and Air Induction/Air Cleaner Housing", Service and Repair
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
- Display readiness code.
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, the readiness code must be generated again.