Mass Air Flow Sensor, Checking
Mass Air Flow Sensor, Checking
Special tools, testers and auxiliary items required
• Multimeter.
• wiring diagram
• Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) Sensor (G70).
Test requirements
• Fuse for Mass Air Flow (MAF) Sensor (G70) 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
Function test
- Connect the scan tool.
- Start engine and let it run at idle.
- Select "Diagnostic mode 1: Check measured values".
- Select measuring value "PID 16: Air stream amount at Mass Air Flow (MAF) sensor".
- Check specified value of air flow quantity at 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 is not obtained:
- check sensor internal resistance:
- values obtained, continue diagnosis
- Values not obtained, replace sensor G70.
- Check wiring of Mass Air Flow (MAF) Sensor (G70 ).
Checking voltage supply
- Disconnect the electrical harness connector - 1 - from the Mass Air Flow (MAF) Sensor (G70).
- Start engine and let it run at idle.
- Using a Multimeter, check the Mass Air Flow (MAF) Sensor (G70) electrical connector terminal 2 to engine Ground (GND) for voltage.
Specified value: battery voltage
- Switch ignition off.
If the specified value is not obtained:
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- Check wiring between Mass Air Flow (MAF) Sensor ( G70) electrical connector terminal 2 and Engine Component Power Supply Relay (J682) for an open circuit.
Specified resistance 1.5 ohms max.
If the specification is not obtained:
- Check the wiring for a short circuit to Battery positive (+) or an open circuit.
Checking wiring
- Using a Multimeter, check the following wiring connection for an open circuit.
Specified resistance 1.5 ohms max.
If the specification is not obtained:
- Check the wiring for a short circuit to Battery positive (+) or an open circuit.
- If necessary, repair the wiring connection.
If no malfunctions are found in the wiring:
- Replace Mass Air Flow (MAF) Sensor (G70).
- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase 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. Refer to => [ Readiness Code ] Readiness Code.
- End diagnosis.
If the DTC does return and no malfunction is detected in the wiring and the voltage supply was 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, Setting ] Readiness Code, Setting.
End of Diagnosis.