Mass Air Flow Sensor, Checking

Special tools and workshop equipment required 

• Multimeter VAG 1526 or Multimeter VAG 1715
• Connector test kit VAG 1594
• Wiring diagram

Test requirements 

• Fuses in E-box (plenum chamber, left) must be OK: Refer to appropriate SYSTEMS WIRING DIAGRAM
  Fig 1: Identifying Fuses In E-Box (Plenum Chamber, Left)

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• The respective fuses of Mass Air Flow (MAF) Sensor -G70- must be OK: appropriate SYSTEMS WIRING DIAGRAM
  Fig 2: Identifying Fuse Box (Instrument Panel, Left)

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Battery voltage must be at least 11.5 volts.
• All electrical consumers such as, lights and rear window defroster must be switched off.
• Parking brake must be engaged or else daylight driving lights will be switched on.
• For vehicles with automatic transmission, selector lever must be in P.
• If vehicle is equipped with an A/C system, it must be switched off.
• Ground (GND) connections between engine and chassis must be OK.
• Coolant temperature must be at least 80° C, Diagnostic mode 1: Check measured values; PID 5, Coolant temperature.

Function test 

-- Connect diagnostic tester.

-- Start engine and let run at idle.

-- Under address word 33, select "Diagnostic mode 1: Checking measured values."

-- Select the measuring value "PID 16: Air flow quantity at Mass Air Flow (MAF) sensor".

-- Check specified value of air flow quantity at Mass Air Flow (MAF) Sensor at idle:

PID		Diagnostic text		Specified value:
16:		Air flow quantity at Mass Air Flow (MAF) sensor Engine running at idle		2.50 to 7.00 g/sec

-- End diagnosis and switch ignition off.

If specified value is obtained, but DTC memory has a DTC concerning Mass Air Flow (MAF) sensor:

-- Check voltage supply of Mass Air Flow (MAF) sensor.

If specified value is not obtained:

-- Check signal and Ground (GND) wires of Mass Air Flow (MAF) sensor.

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.

Specified value: at least 11.0 V

-- Switch ignition off.

If there is no voltage:

-- Check voltage supply at 5-pin connector terminal 2 according to wiring diagram: Refer to appropriate SYSTEMS WIRING DIAGRAM

-- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

-- Generate readiness code.

If voltage supply and wires are OK:

-- Connect multimeter to terminal 4 of connector and engine Ground (GND) for voltage measurement.

-- Switch ignition on.

Specified value: at least 4.5 V

-- Switch ignition off.

If there is no voltage:

-- Check signal and Ground (GND) wires of Mass Air Flow (MAF) sensor.

Checking signal and Ground wires of Mass Air Flow (MAF) Sensor

-- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor -G70- with Intake Air Temperature (IAT) Sensor -G42- (arrow).

-- Connect test box.

-- Check wires between test box and 5-pin connector for open circuit according to wiring diagram.

Terminal 3 + socket 27

Terminal 4 + socket 53

Terminal 5 + socket 29

Wire resistance: max. 1.5 Ω

-- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.

Specified value: ∞ Ω

-- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

-- Generate readiness code.

If no DTCs are found in wires:

-- Replace Mass Air Flow (MAF) Sensor -G70-.

Final Procedures 

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .