Mass Air Flow Sensor G70, Checking

Mass Air Flow Sensor G70, 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 SC22 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. 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:

Diagnostic text Specified value
Air flow quantity at
Mass Air Flow (MAF) sensor
Engine running at idle 3.00 to 6.00 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 Mass Air Flow (MAF) Sensor G70 electrical circuit.

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 3 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 3 to the Power Supply Relay 2 (terminal 15) J681 terminal 2 for an open circuit.

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 connectors 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 Ground (GND)







- Using a multimeter, check the Mass Air Flow (MAF) Sensor G70 electrical harness connector terminal 2 to Ground (GND) connection 1 (on firewall) for resistance.

Specified value: 1.5 Ohms max.

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND) or an open circuit.
- 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:

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 terminal 1 to the Motronic Engine Control Module (ECM) J623 electrical harness connector T94 terminal 22 for an open circuit.

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

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 the Mass Air Flow (MAF) Sensor G70.
- Erase the 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. Monitors, Trips, Drive Cycles and Readiness Codes
- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not 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. 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. Monitors, Trips, Drive Cycles and Readiness Codes

End of Diagnosis