Air Flow Meter/Sensor: Testing and Inspection
Mass Air Flow (MAF) 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.
NOTE: Use only gold-plated terminals when servicing terminals in harness connector.
Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram
Requirement
- The respective fuses of Diesel-Direct fuel injection system must be OK:
- Battery voltage must be at least 11.5 volts.
- All electrical consumers such as, lights and rear window defroster must be switched off.
- For vehicles with automatic transmission, selector lever must be in -P-.
- Parking brake must be engaged.
- 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 degrees C, Diagnostic mode 1: Check measured values; PID 5, Coolant temperature. Diagnostic Mode 1: Check Measuring Values
Function test
- Connect diagnostic tester. Diagnostic Tester, Connecting
- 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 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: 4.5 to 9.0 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 wires to Engine Control Module (ECM) according to wiring diagram.
Voltage supply for Mass Air Flow (MAF) sensor, checking
- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor -G70- (arrow).
- Switch ignition on.
- Measure voltage supply for MAF sensor between the following connector terminals:
Connector on Mass Air Flow (MAF) sensor -G70- terminal Specified value:
2 + Ground (GND) approx. battery voltage
2 + 3 approx. battery voltage
4 + Ground (GND) approx. 5 V
4 + 3 approx. 5 V
- 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 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If specified values are not obtained:
- Check wires to Engine Control Module (ECM) according to wiring diagram.
Check wires to control module
- Connect test box (1598/42) to Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- wiring harness using adapter cable (V.A.G 1598/392), connecting test box for wiring test. Test Box, Connecting For Wiring Test
- Check for open circuits in wires between test box and harness connector according to wiring diagram.
Terminal 3 + socket 60
Terminal 4 + socket 40
Terminal 5 + socket 82
Wire resistance: max. 1.5 Ohms
- Check wire from 5-pin connector terminal 2 to CIS Engine Control Module (ECM) Fuse -S31- in fuse holder according to wiring diagram:
- 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 Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-.