Mass Air Flow Sensor G70/Intake Air Temperature Sensor G42, Checking

Mass Air Flow Sensor G70/Intake Air Temperature Sensor G42, Checking

• The Intake Air Temperature Sensor G42 is part of the Mass Air Flow Sensor G70 and cannot be replaced separately.

• 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 (SB10) 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 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 - 3 -.





- 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 Motronic Engine Control Module (ECM) Power Supply Relay (J271) terminal 2/87 for an open circuit, a short circuit to each other, Battery (+), or Ground (GND).

If no malfunction is found in the wiring and the voltage supply 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 Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module J623, Replacing ] Engine Control Module J623, Replacing.

- Using a multimeter, check the Mass Air Flow (MAF) Sensor (G70) electrical harness connector terminals to the Engine Control Module (ECM) (J623) electrical harness connector T121 terminals for resistance.









Specified value: 1.5 ohms max.

If the specification was 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 found in the wiring and if the voltage supply was OK:

- Replace 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 Description ] Readiness Code Description.

- End diagnosis.

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

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

- Assembly is performed in the reverse of the removal.

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. Refer to => [ Readiness Code ] Readiness Code.

End of diagnosis