With Generic Scan Tool

Mass Air Flow (MAF) 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
- The Mass Air Flow (MAF) Sensor G70 fuse OK.
- The 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 � C.
- Ignition switched off.

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

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:






- End diagnosis and switch ignition off.

If specified value is obtained, but DTC memory has a DTC concerning Mass Air Flow (MAF) Sensor G70 :
- Check voltage supply of 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 - arrow -.
- 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) Relay J17 terminal 23/87 for an open circuit.
Specified value: 1.5 Ohms max.

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 engine Ground (GND) for resistance.
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, lose 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 Test Box 105 Pin VAG1598/31.

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






- 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 T121 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 connector for damage, corrosion, lose 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.
- Erase the DTC memory. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- 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 OK:
- Replace the MFI Engine Control Module (ECM) J220. Service and Repair
- Assembly is performed in the reverse of the removal.

Final procedures
After the repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.

End diagnosis