Air Flow Meter/Sensor: Testing and Inspection
Mass Air Flow Sensor G70, 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)/Intake Air Temperature (IAT) Sensor (G42) Fuse 10 (on fuse panel B) (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.
Specified value: 1.5 ohms max.
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 105 Pin (VAG1598/31).
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 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).
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 Description.
End of diagnosis