Air Flow Meter/Sensor: Testing and Inspection
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 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 idle.
- Using the scan tool, Check the air flow quantity of the Mass Air Flow (MAF) Sensor (G70) at idle:
- Switch the ignition OFF.
If the specified value was obtained:
- Condition may be intermittent
- Check the wiring for an open, high resistance or short to ground.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
- Go to Final procedures
If the specified value was Not obtained:
- Disconnect the Mass Air Flow (MAF) Sensor (G70) electrical harness connector - 1 -.
- Using a Multimeter, Check the Mass Air Flow (MAF) Sensor (G70) electrical harness connector terminal 3 to Ground (GND) for voltage.
Specified value: Battery Voltage
- Switch the ignition OFF.
- Continue test according to the following table:
Checking wiring
- Remove the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service manual.
- Using a Multimeter, Check the Mass Air Flow (MAF) Sensor (G70) electrical harness connector to the Motronic Engine Control Module (ECM) electrical harness connector T94 for an open circuit.
Specified value: 1.5 ohms Max.
If the specified value was Not obtained:
- Check the wiring connection for an open or short circuit.
- Check the wiring connection for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection and replace any open fuses
- Go to Final procedures
If the specified value was obtained:
- If necessary, repair any faulty wiring or connections, If no faults were found Replace the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service manual.
- Go to Final procedures
Checking wiring
- Remove the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service manual.
- Using a Multimeter, Check the Mass Air Flow (MAF) Sensor (G70) electrical harness connector to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T94 for an open circuit.
Specified value: 1.5 ohms Max.
If the specified value was Not obtained:
- Check the wiring connection for an open circuit, short circuit to Battery positive or Ground
- Check the wiring connection for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
- Go to Final procedures
If the specified value was obtained:
- Replace the Mass Air Flow (MAF) Sensor (G70). Refer to appropriate service manual.
Final procedures
- Reinstall the engine cover and Air Filter Housing, if necessary. Refer to the appropriate service manual.
- 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 Modes 01 - 0A.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 0A.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Programming and Relearning.