Air Flow Meter/Sensor: Testing and Inspection

Diagnostic Procedures

Mass Air Flow Sensor, Checking

• 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

• The Mass Air Flow (MAF) Sensor (G70) fuse 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 connections between engine/transmission/chassis OK.

• Coolant Temperature at least 80° C.

• Ignition switched off.

Test procedure

- Observe safety precautions. Refer to => [ Safety Precautions ] Safety Precautions

- Observe Clean Working Conditions. Refer to => [ Clean Working Conditions ] Clean Working Conditions

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] 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:





- 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). Refer to the Repair Information.

- 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.





Specified value: 1.5 ohms 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 ] Diagnostic Modes 01 - 09.

- Perform a road test to verify repair.

If the DTC does not return:

Generate readiness code. Refer to => [ Readiness Code ] 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). Refer to the Repair Information.

- 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 ] Diagnostic Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.