Mass Air Flow Sensor, Checking

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirements 

• The Mass Air Flow (MAF) Sensor -G70- fuse OK.
  Fig 1: Fuses On E-Box In Engine Compartment, Left Side

  Courtesy of VOLKSWAGEN UNITED STATES, INC.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, shift selector lever into position "P" or "N".
• A/C switched off.
• Ground connections between engine/transmission/chassis OK.
• Coolant Temperature at least 80° C.
• Ignition switched off.

Test procedure 

-- Observe safety precautions. Refer to SAFETY PRECAUTIONS 

-- Observe Clean Working Conditions. Refer to CLEAN WORKING CONDITIONS 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .

Start diagnosis 

Function test 

-- Connect the scan tool.

-- Start engine and let it run at idle.

-- Using the scan tool, Check the air flow quantity of the Mass Air Flow (MAF) Sensor -G70- at idle:

Diagnostic text		Specified value
Air flow quantity at Mass Air Flow (MAF) sensor
Engine running at idle		2.00 to 5.00 g/sec

-- Switch ignition off.

If the specified value was obtained, but the DTC memory has a DTC concerning the Mass Air Flow (MAF) Sensor -G70-:

-- Check the voltage supply of the Mass Air Flow (MAF) Sensor -G70-.

If specified value was not obtained:

Checking Voltage: 

-- Disconnect the Mass Air Flow (MAF) Sensor -G70- electrical harness connector.

-- Start the engine and let it run at idle.

-- Using a multimeter, check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 5 to engine ground.

Specified value: battery voltage.

-- Switch the ignition off.

If specified value was not obtained:

-- Check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 5 to fuse 10 in Fuse Panel C for high resistance, an open or short to ground.

If no malfunction is detected in the wiring and if the voltage supply was OK:

Checking electrical circuit: 

If the manufacturers test box is being used. Perform the following step.

-- Install the test box.

If the manufacturers test box is not being used. Perform the following step.

-- Remove the Motronic Engine Control Module (ECM) -J623-.

-- Using a multimeter, check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminals to the Motronic Engine Control Module (ECM) -J623- electrical harness connector T94 terminals for an open circuit.

Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminals	Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminals or test box socket
1	22
2	42
3	13
4	64

Specified value: 1.5 Ω max.

If the specification was not obtained:

-- Check the wiring for high resistance, an open or a short to voltage or ground.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

-- If necessary, repair the faulty wiring connection.

-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .

-- Perform a road test to verify repair.

If the DTC does not return:

Generate readiness code. Refer to READINESS CODE .

If the DTC does return, no malfunction is detected in the wiring and the voltage supply is OK:

-- Replace the Motronic Engine Control Module (ECM) -J623-.

-- Assembly is performed in the reverse of the removal.

Final procedures 

After repair work, the following work steps must be performed in the mentioned 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 .