Mass Air Flow Sensor, Checking
Mass Air Flow Sensor, 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) fuse 1 in Fuse box C is 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:
If specified value is obtained, but DTC memory has a DTC concerning Mass Air Flow (MAF) Sensor (G70):
- Check for intermittent connections or rub through of harness.
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 2 to engine Ground (GND).
Specified value: battery voltage.
- Switch the ignition off.
If specified value was not obtained:
- Remove the fuse 1 in Fuse box C. Check the Mass Air Flow (MAF) Sensor (G70) electrical harness connector terminal 3 to Fuse 1 in Fuse box C for an open circuit, high resistance or a short to ground.
Specified value: 1.5 ohms max.
- Repair the harness and replace the fuse as necessary.
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.
If the manufacturers test box is not being used, perform the following step.
- Remove the Motronic Engine Control Module (ECM) (J623). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.
- 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 T121 terminals for an open circuit.
If the specified values were not obtained:
- Check the wiring for an open, high resistance or short to ground. Use the following table as a guide.
- 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 Mass Air Flow (MAF) Sensor (G70)24 Fuel Injection System
If no malfunction is detected in the wiring and if the voltage supply was not OK:
- Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.
Final procedures
After the 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.