P1424

What the Code Means

Code P1424 sets when the mass air flow sensor (MAF) reports an air flow value to the engine control unit (DME) that exceeds the calculated value. The DME relies on MAF readings to calculate the amount of fuel injected, so an inflated value skews the air-fuel mixture — it runs rich or lean, which affects performance, fuel economy, and emissions.

The causes of high readings can be in the sensor itself or upstream of it: a faulty MAF, a dirty air filter, a vacuum leak in the intake tract, or other intake system problems.

Symptoms

• Check Engine light comes on;
• reduced engine power;
• increased fuel consumption;
• rough idle;
• hard starting (long crank).

Diagnosis and Repair

Start with the simple checks and work up, ruling out one cause at a time:

1. Check the air filter and clean or replace it if needed — dirt skews MAF readings.
2. Clean the MAF sensor; if readings don't recover, replace the sensor (OEM BMW 13621433077).
3. Inspect the intake system for vacuum leaks — unmetered air changes the calculated mixture.
4. Check the fuel system: injectors and fuel pressure regulator.
5. After fixing the cause, reset the DME adaptations by disconnecting the battery for 10 minutes and confirm the code doesn't return.

Secondary Damage

If you ignore the code, the incorrect air-fuel mixture sends unburned fuel into the exhaust: the catalytic converter (OEM 18307558279) overheats and gets damaged. Carbon deposits also build up on the valves, shortening engine life. Skipping diagnosis is a bad bet — a new catalytic converter costs far more than a timely check of the MAF sensor and intake tract.