Mass Air Flow Sensor, Checking

Mass Air Flow Sensor, Checking

The following procedure is used to diagnose the Mass Air Flow (MAF) Sensor (G70) which is controlled by Motronic Engine Control Module (ECM) (J623).

• 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 Fuse (SA15) 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 (GND) connections between engine/transmission/chassis OK.

• Coolant Temperature at least 80 °C.

• Ignition switched off.

Test procedure

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

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:





- End diagnosis and switch ignition off.

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

- 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

- Remove the engine compartment trim.

- Remove the engine cover.

- Disconnect the Mass Air Flow (MAF) Sensor (G70) electrical harness connector - 3 -.





- Crank the engine.

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





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) Relay (J17) socket 20/87 for an open circuit or a short circuit to Ground (GND).

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

If no malfunction is detected in the wiring and 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 => [ Engine Control Module, Removing and Installing ] Engine Control Module, Removing and Installing.

- 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 terminals for resistance.









Specified value: 1.5 ohms max.

If any of the specified values were not obtained:

- Check the wiring for an open circuit, a short circuit to each other, Battery (+), or 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 the Mass Air Flow (MAF) Sensor (G70)

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End diagnosis.

If the DTC returns and no malfunction is found in the wiring and voltage supply was OK:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

Assembly is performed in the reverse order of the removal, note the following:

Final procedures

After 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 ] Diagnostic Mode 03 - Read DTC Memory.

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

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