Mass Air Flow Sensor, Checking

Mass Air Flow Sensor, Checking

NOTE: Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) Sensor G70.

Special tools, testers and auxiliary items required
- Multimeter.
- Wiring diagram.

Test requirements
- Fuse (on fuse panel) S243 OK.
- Fuel Pump (FP) Relay J17 OK.
- 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 (GND) connections between engine/transmission/chassis OK.
- Coolant Temperature at least 80 degrees C.
- Ignition switched off.

Test procedure
- Perform a preliminary check to verify the customers complaint. General Diagnosis

Start diagnosis
- 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 2.50 to 7.00 g/sec

- End diagnosis and 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:
- Check the wiring of the Mass Air Flow (MAF) Sensor G70.

Checking voltage supply







- Disconnect the Mass Air Flow (MAF) Sensor G70 electrical harness connector -1 -.
- Start the engine and let it run at idle.







- Using a multimeter, check the Mass Air Flow (MAF) Sensor G70 electrical harness connector terminal 2 to engine Ground (GND).

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 2 to the Fuel Pump (FP) 2 Relay J49 terminal 2/87 for an open circuit, a short circuit to each other, Battery (+), and Ground (GND).
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.

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 VAG1598/31.

If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) J220.







- Using a multimeter, check the Mass Air Flow (MAF) Sensor G70 electrical harness connector terminals to the Motronic Engine Control Module (ECM) J220 electrical harness connector terminals for resistance.

Mass Air Flow (MAF) Sensor Motronic Engine Control Module (ECM) J220
G70 electrical harness electrical harness connector terminals
connector terminals or test box socket
1 26
3 27
4 53
5 29

Specified value: 1.5 Ohms max.

If the specification was not obtained:
- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:
- Replace Mass Air Flow (MAF) Sensor G70.

Final procedures
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code.

End of diagnosis