With Generic Scan Tool
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 less fuel may be injected.
NOTE: Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) sensor.
Recommended special tools and equipment
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram
Test requirement
- The respective fuses of Mass Air Flow (MAF) Sensor -G70- 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 position -P- or -N-.
- 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 degree C, Diagnostic mode 1: Check measuring values; PID 5, Coolant temperature. Diagnostic Mode 1: Check Measured Values
Function test
- Connect diagnostic tester. Diagnostic Tester, Connecting
- Start engine and let run at idle.
- 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: 2.80 to 5.30 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.
Voltage Supply For Mass Air Flow (MAF) Sensor, Checking
- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor (arrow).
- Switch ignition on.
- Measure voltage supply for MAF sensor between the following connector terminals:
Connector at Mass Air Flow(MAF) Sensor Specified value
-G70-Terminal
2 + Ground (GND) approx. battery voltage
2 + 3 approx. battery voltage
4 + Ground (GND) about 5 V
4 + 3 about 5 V
If specified values are obtained:
- Replace Mass Air Flow (MAF) Sensor -G70-:
- Erase DTC memory of control module for Diesel-Direct fuel injection system, 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 signal and Ground (GND) wire of Mass Air Flow (MAF) sensor.
Checking signal and Ground wires of Mass Air Flow (MAF) Sensor
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test
Vehicles with 80-pin control module
- Check for open circuit in wires between test box and harness connector according to wiring diagram.
Terminal 2 + socket 2
Terminal 2 + socket 28
Terminal 3 + socket 4
Terminal 4 + socket 50
Terminal 5 + socket 52
Wire resistance: max. 1.5 Ohm
Vehicles with 121-pin control module
- Check for open circuit in wires between test box and harness connector according to wiring diagram.
Terminal 2 + socket 1 and 2
Terminal 3 + socket 49
Terminal 4 + socket 30
Terminal 5 + socket 68
Wire resistance: max. 1.5 Ohm
Continuation for all vehicles
- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: Infinite Ohm
If no malfunctions are detected in wires:
- Replace Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes