Mass Air Flow Sensor, Checking

Special tools and workshop equipment required 

• Multimeter VAG1526 or multimeter VAG1715
• Connector test kit VAG1594
• Wiring diagram

Test requirements 

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

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Motronic Engine Control Module (ECM) Power Supply Relay -J271- must be OK, check: Refer to SYSTEM WIRING DIAGRAM
• Respective fuses of Mass Air Flow (MAF) Sensor -G70- and Mass Air Flow (MAF) Sensor 2 -G246- in fuse box (instrument panel, left) must be OK: Refer to SYSTEM 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, for example, 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 position.
• 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		1.00 to 3.00 g/sec

-- End diagnosis and switch ignition off.

If specified value is obtained, but a DTC concerning Mass Air Flow (MAF) sensors 1 and 2 is stored in DTC memory:

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

If specified value is not obtained:

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

Voltage supply of Mass Air Flow (MAF) sensors, checking 

Cylinder bank 1 

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

Cylinder bank 2 

-- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor 2 -G246- (arrow).

Cylinder bank 1 and 2 

-- 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 SYSTEM 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 wires and Ground (GND) wires 

Cylinder bank 1 

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

Cylinder bank 2 

-- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor 2 -G246- (arrow).

Cylinder bank 1 and 2 

-- Connect test box to control module wiring harness, connect test box for wiring test.

-- Check wires between test box and °-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Wire resistance: max. 1.5 Ω

Cylinder bank 1 

Component	Connector	Test box
Mass Air Flow (MAF) Sensor 1	Terminal 3	Socket 27
	Terminal 4	Socket 53
	Terminal 5	Socket 29

Cylinder bank 2 

Component	Connector	Test box
Mass Air Flow (MAF) Sensor 2	Terminal 3	Socket 27
	Terminal 4	Socket 53
	Terminal 5	Socket 109

Cylinder bank 1 and 2 

-- 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 the respective Mass Air Flow (MAF) Sensor.:

Cylinder bank 1 

• Mass Air Flow (MAF) Sensor -G70- with Intake Air Temperature (IAT) Sensor -G42-.

Cylinder bank 2 

• Mass Air Flow (MAF) Sensor 2 -G246-.

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

-- Generate readiness code.