Air Flow Meter/Sensor: Testing and Inspection
Mass Air Flow (MAF) Sensor, Checking
NOTE: Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) sensor.
Special tools and equipment
- VAG1551 scan tool (or VAG1552 mobile scan tool) with VAG1551/3B cable
- VAG1598/31 test box
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram
Test requirements
- All fuses must be OK.
- Battery voltage must be at least 11.5 volts.
- Fuel Pump (FP) relay must be OK.
- All electrical consumers like, for example, lights and rear window heating must be switched off.
- If vehicle is equipped with an A/C system, it must be switched off.
- For vehicles with automatic transmission, selector lever must be in -P- or -N-.
- Coolant temperature must be at least 85 °C, See display group 04, display field 3
Test sequence
- Connect VAG1551 scan tool (VAG1552). Start engine and select the Engine Control Module (ECM) using address word 01.
Connecting scan tool and selecting ECM. 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 -8- to select "Read measuring value block" function 08. Press -Q- button to confirm input.
Indicated on display:
Read measuring value block
Enter display group number XXX
- Press 0, 0 and 2 for the function "display group number 2", and then press Q to exit from input mode.
Indicated on display: (1 to 4 = display fields)
Read measuring value block 2 ->
1 2 3 4
- Check intake of mass air in display field 4.
Display Group 2:
- If the specified value is not obtained or there is still a DTC in DTC memory regarding the Mass Air Flow (MAF) sensor, check voltage supply and the signal and Ground (GND) wire of the Mass Air Flow (MAF) sensor.
If specified value is obtained:
- Press the -> button.
- Press buttons -0- and -6- to select "End Output" function 06. Press -Q- button to confirm input.
- Switch ignition off.
Evaluation display group 2, display field 4 mass air taken in
Voltage supply for Mass Air Flow (MAF) sensor, checking
- Disconnect 5-pin connector from Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42- (arrow).
- Connect multimeter to terminal 2 of connector and engine Ground (GND) for voltage measurement.
- Start engine, and let run at idle. Specification: 11.0 to 15.0 V
If there is no voltage:
- Switch ignition off.
- Check wire between 5-pin connector terminal 2 and the Fuel Pump (FP) relay -J17- for open circuit according to wiring diagram. Wire resistance: max: 1.5 Ohms
If voltage supply and wires are OK:
- Connect multimeter to terminal 4 of connector and engine Ground (GND) for voltage measurement.
- Switch ignition on. Specification: at least 4.5 V
If there is no voltage:
- Switch ignition off.
- Check signal and ground wires.
Checking Signal and Ground Wires for Mass Air Flow (MAP) Sensor
- Connect VAG1598/31 test box to control module wiring harness. Engine Control Module (ECM) is not connected.
- Check wires between test box and 5-pin connector for open circuits according to wiring diagram.
Terminal 5 + socket 29
Terminal 4 + socket 53
Terminal 3 + socket 27
Wire resistance: max: 1.5 Ohms
- Also check all wires for short circuit to each other. Specification: Infinity Ohms
- Also check wires for shorts to battery B+ or Ground (GND).
If no DTCs are found in wires:
- Replace Mass Air Flow (MAF) sensor -G70-.
- Check DTC memory, repair any malfunctions and then erase DTC memory.
After successful repair:
- Read readiness code. If DTC memory was erased or the Engine Control Module (ECM) was disconnected from the continuous B+ supply, the readiness code must be re-generated. Refer to Monitors, Trip and/or Drive Cycle (Readiness Codes)/Reading Readiness Code. Testing and Inspection Refer to Monitors, Trip and/or Drive Cycle (Readiness Codes)/Generating Readiness Code. Testing and Inspection