Mass Air Flow Sensor, Checking

Observe all safety precautions: SAFETY PRECAUTIONS 

View clean working conditions: CLEAN WORKING CONDITIONS 

Prior to repair work, perform a preliminary check to verify the condition. Refer to PRELIMINARY CHECK .

Special Tools And Workshop Equipment Required 

• Multimeter.
• Wiring diagram.

Test Requirements 

• The Mass Air Flow (MAF) Sensor -G70- fuse 1 in Fuse Panel 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 connections between engine/transmission/chassis OK.
• Coolant Temperature at least 55° C.
• Ignition switched Off.

Test Procedure 

-- Perform a preliminary check to verify the customers complaint. Refer to 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:

Diagnostic text		Specified value
Air flow quantity at Mass Air Flow (MAF) sensor
Engine running at idle		6.50 to 8.2 g/sec.

If The Specified Value Was Obtained: Condition Is Not Present At This Time. 

-- Check the electrical harness connector at the ECM and sensor for damage, corrosion, loose or broken terminals.

-- Check the intake duct for air leaks, loose connections.

If The 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 5 to engine Ground for voltage.

Specified Value: Battery Voltage. 

-- Switch the ignition OFF.

If the specified value was Not obtained:

-- Remove fuse 1 (2010 Models) or fuse 15 (2011 Models) in Fuse Panel C. Refer to Appropriate Wiring Diagrams for fuse locations. Check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 5 to Fuse 1 or 15 in Fuse Panel C for an open circuit, high resistance or short to ground.

Specified Value: 1.5 Ω Max. 

-- If necessary, repair the faulty wiring connection.

If The Specified Value Was Obtained: 

Checking electrical circuit

-- Start the engine and let it run at idle.

-- Using a multimeter, connect black lead to ground and red lead to terminal 1, 2 and 4 of the MAF connector and check for voltage using the chart below.

Specified Values: 

Mass Air Flow (MAF) Sensor -G70- terminal:	Specified voltage
1	4.94 V (+/-.5 V)
2	4.97 V (+/-.5 V)
4	Near 0 V

-- Switch the ignition OFF.

If The Specified Value Was Not Obtained: 

Checking wiring

-- Remove the Motronic Engine Control Module (ECM) -J623-.

-- 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 T94 terminals for an open circuit. Refer to Appropriate Wiring Diagrams for Pin locations.

Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminals	Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminals
1	18
2	23
4	39

Specified Value: 1.5 Ω Max. 

If The Specified Value Was Not Obtained: 

-- Check the wiring for an open, high resistance or short circuit.

-- 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- Refer to the Repair information.

If No Malfunction Is Detected In The Wiring And The Voltage Supply Was Not OK: 

-- Replace the Motronic Engine Control Module (ECM) -J623-.

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 .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .