Mass Air Flow (MAF) Sensor, Checking

Mass Air Flow (MAF) sensor, checking

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 requirements

- Fuses in E-box (in plenum chamber, left) must be OK:
- Motronic Engine Control Module (ECM) Power Supply Relay - J271 - -position A3- must be OK, check:

- Respective fuses of Mass Air Flow (MAF) Sensor - G70 - and Mass Air Flow (MAF) Sensor 2 - G246 - in fuse box (instrument panel, 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.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in - P - position.
- 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.

Function test
- Connect diagnostic tester.
- Start engine and let run at idle.
- Under address word 33, select "Diagnostic mode 1: Checking 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:

- End diagnosis and switch ignition off.

If specified value is obtained, but a DTC concerning Mass Air Flow (MAF) sensors 1 and 2 is stored in DTC memory:
- Check voltage supply of Mass Air Flow (MAF) sensors.

If specified value is not obtained:
- Check signal wires and Ground (GND) wires of Mass Air Flow (MAF) sensors.

Voltage supply of Mass Air Flow (MAF) sensors, checking

Cylinder bank 1

- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor - G70 - with Intake Air Temperature (IAT) Sensor - G42 - arrow.

Cylinder bank 2

- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor 2 -G246- (arrow).

Cylinder bank 1 and 2

NOTE:
- Cylinder bank 1 = in driving direction, right
- Cylinder bank 2 = in driving direction, left

- Connect multimeter to terminal 2 of connector and engine Ground (GND) for voltage measurement.
- Start engine, and let run at idle.

Specified value: at least 11.0 V

- Switch ignition off.

If there is no voltage:
- Check voltage supply at 5-pin connector terminal 2 according to wiring diagram
- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If voltage supply and wires are OK:

- Connect multimeter to terminal 4 of connector and engine Ground (GND) for voltage measurement.
- Switch ignition on.

Specified value: at least 4.5 V

- Switch ignition off.

If there is no voltage:
- Check signal and Ground (GND) wires of Mass Air Flow (MAF) sensor.

Checking signal wires and Ground (GND) wires of Mass Air Flow (MAF) Sensors

Cylinder bank 1

- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor - G70 - with Intake Air Temperature (IAT) Sensor -G42- arrow.

Cylinder bank 2

- Check wires between test box and � -pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Wire resistance: max. 1.5 ohms

Cylinder bank 1

Cylinder bank 2

Cylinder bank 1 and 2
- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.

Specified value: infinity ohms.

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If no DTCs are found in wires:
- Replace the respective Mass Air Flow (MAF) Sensor.:

Cylinder bank 1
- Mass Air Flow (MAF) Sensor -G70- with Intake Air Temperature (IAT) Sensor -G42-.

Cylinder bank 2
- Mass Air Flow (MAF) Sensor 2 -G246-.

NOTE:
- Cylinder bank 1, in direction of travel, right.
- Cylinder bank 2, in direction of travel, left.

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes