Why do MAFs fail ?
A – The surface of the thin platinum wire can become contaminated with oil vapour from the engine. This contamination will cause the sensor to output incorrect voltages. To eliminate any possible deposits on the wire, it undergoes a “burn off” cycle every time the engine is switched off if the engine temperature is above 60 degrees C. and the engine has been above 2000 rpm. Approximately 4 seconds after the engine is stopped, the wire is heated to 1,000 degrees C for about 1 second. The 4 second delay assumes that the engine is unlikely to be re-started while the burn off is in progress, as any airflow past the wire when heated to this temperature would accelerate the surface erosion of the wire due to reaction with the oxygen in air. Unfortunately, some erosion does occur with each burn off cycle, even with these precautions. A car that has covered 80,000 miles may have had as many as 8,000 burn off cycles activated. Eventually, due to the erosion of the hot wire, the MAF’s output wil
