Air Flow Meter/Sensor: Testing and Inspection
Diagnostic Procedures
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
• Fuse (SB44) OK.
• The Fuel Primer Relay (J643) 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 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:
- 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:
Checking voltage supply
- Disconnect the Mass Air Flow (MAF) Sensor (G70 ) electrical harness connector.
- 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 Ground.
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 Relay (J17) socket 23/87 for an open circuit or short to Ground. NOTE: Fuse S-243 is also part of this circuit and may be open if circuit is shorted. See Wiring Diagram for circuit details.
- 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 the voltage supply is 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) ( J220). Refer to the Repair Information.
- 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 terminals 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 (+) or Ground.
- 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 the voltage supply was OK:
- Replace Mass Air Flow (MAF) Sensor (G70).
- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09
- Perform a road test to verify repair.
If the DTC does not return:
Generate readiness code. Refer to => [ Readiness Code ] Readiness Code.
If the DTC does return, no malfunction was detected in the wiring and the voltage supply was OK:
- Replace the Motronic Engine Control Module (ECM) (J220). Refer to the Repair Information.
- 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. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.