Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Function test
- Connect diagnostic tester. Refer to Diagnostic tester, connecting .
- 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:
Vehicles with engine code ALH:
Specified value: 2.80 to 5.30 g/sec
Vehicles with engine code BEW:
Specified value: 1.80 to 4.30 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. Refer to Voltage supply for Mass Air Flow (MAF) sensor, checking .
If specified value is not obtained:
- Check signal and Ground (GND) wires of Mass Air Flow (MAF) sensor. Refer to Checking signal and Ground wires of Mass Air Flow (MAF) Sensor .
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.