Air Flow Meter/Sensor: Testing and Inspection
Diagnostic Procedures
Mass Air Flow Sensor, Checking
The Mass Air Flow (MAF) sensor signal is used by the control module to calculate the permissible injection quantity and to regulate Exhaust Gas Recirculation (EGR). The smaller the MAF sensor signal is, the lesser fuel may be injected.
• Cylinder bank 1 is located in direction of travel, right.
• Cylinder bank 2 is located in direction of travel, left.
• Use only gold-plated terminals when servicing terminals in harness connector.
Special tools, testers and auxiliary items required
• Multimeter (VAG1526) or Multimeter (VAG1715)
• Connector test kit (VAG1594)
• Wiring diagram
Test Prerequisites
• Fuses in E-box (plenum chamber, left) must be OK:
• Battery voltage must be at least 11.5 volts.
• All electrical consumers such as, for example, lights and rear window defroster must be switched off.
• For vehicles with automatic transmission, selector lever must be in P.
• If vehicle is equipped with an A/C system, it must be switched off.
• Ground (GND) connections between engine and chassis must be OK.
• Coolant temperature must be at least 80°C --> [ Diagnostic Mode 01 - Read Current System Data ] .
Mass Air Flow Sensor 1, Test Sequence
Function Test
- Connect diagnostic tester.
- Start engine and let run at idle.
- Depress accelerator pedal to approx. 1500 RPM.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select the measuring value "PID 16: Air flow quantity at Mass Air Flow (MAF) sensor".
- Check specified value of air flow quantity at Mass Air Flow (MAF) Sensor at idle:
Specified value: 4.50 to 7.00 g/sec
- End diagnosis and switch ignition off.
If specified value is obtained, but DTC memory has a DTC concerning Mass Air Flow (MAF) sensor:
- Check voltage supply of Mass Air Flow (MAF) sensor.
If specified value is not obtained:
- Check signal and Ground (GND) wires of Mass Air Flow (MAF) sensor.
Checking Voltage Supply
- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor (G70) (- B -).
- Switch ignition on.
- Measure voltage supply for MAF sensor between the following connector terminals:
- Switch ignition off.
If specified values are obtained:
- Replace Mass Air Flow (MAF) Sensor (G70).
- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ]
- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
If specified values are not obtained, check Signal and Ground Wires
Checking Signal and Ground Wires
- Connect test box ((VAG1598/42)) to Engine Control Module (ECM) (J623) wiring harness using adapter cable ((VAG1598/39-2)) , connecting test box for wiring test.
- Check wires between test box and harness connector for open circuit according to wiring diagram.
Terminal 2+socket 18
Terminal 3 + socket 60
Terminal 4 + socket 40
Terminal 5 + socket 82
Wire resistance: max. 1.5ohms
- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: infinite ohms
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM) (J623) --> [ Engine Control Modules, Replacing ].
Mass Air Flow Sensor 2, Test Sequence
Function Test
- Connect diagnostic tester.
- Start engine and let run at idle.
- Depress accelerator pedal to approx. 1500 RPM.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select the measuring value "PID 16: Air flow quantity at Mass Air Flow (MAF) sensor".
- Check specified value of air flow quantity at Mass Air Flow (MAF) Sensor at idle:
Specified value: 4.50 to 7.00 g/sec
- End diagnosis and switch ignition off.
If specified value is obtained, but DTC memory has a DTC concerning Mass Air Flow (MAF) sensor:
- Check voltage supply of Mass Air Flow (MAF) sensor.
If specified value is not obtained:
- Check signal and Ground (GND) wires of Mass Air Flow (MAF) sensor.
Checking Voltage Supply
- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor 2 (G246) (- A -).
- Switch ignition on.
- Measure voltage supply for MAF sensor between the following connector terminals:
- Switch ignition off.
If specified values are obtained:
- Replace Mass Air Flow (MAF) Sensor 2 (G246).
- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] .
- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
If specified values are not obtained:
- Check signal and Ground (GND) wires of Mass Air Flow (MAF) sensor.
Checking Signal and Ground Wires
- Connect test box ((VAG1598/42)) to Engine Control Module 2 (J624) wiring harness using adapter cable ((VAG1598/39-2)) , connecting test box for wiring test.
- Check wires between test box and harness connector for open circuit in according to wiring diagram.
Terminal 2+socket 18
Terminal 3 + socket 60
Terminal 4 + socket 40
Terminal 5 + socket 82
Wire resistance: max. 1.5ohms
- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: infinite ohms
If no malfunctions are found in wires:
- Replace Engine Control Module 2 (J624).