The fault is then designated as “debounced” (confirmed) and is saved as an OBD fault. The lamp only illuminates when the same fault occurs again during the next drive cycle or within a certain period. If a fault is detected in a driving cycle that influences the exhaust gas, it is saved as a “non-debounced” fault, meaning that the malfunction indicator lamp does not illuminate. Not every fault detected by the OBD leads directly to a malfunction indicator lamp illuminating. Pulsations and return flows can also be detected in newer designs with two separate measurement bridges. This method takes account of the density of the inflowing air. This heating current is the measurement for the inflowing air mass. The control electronics counter- balance this cooling by means of a heating current. The air cools the hot-film sensor as it flows in. Temperature (depending on vehicle manufacturer). This hot-film sensor is heated to a constant temperature of approx. Newer models work with a film-like heating resistor on a mount.

Any contaminations on the hot-wire are burnt off by briefly heating it up after switching off the engine.

Older models have a hot-wire sensor element. Both versions – with or without tube – are referred to as air mass sensors. The complete air mass sensor consists of a flow passage (tube), in which the intake air flows past the sensor unit itself.ĭepending on application and vehicle, the air mass sensor is available as a single plug-in module, or fully integrated min a plastic tube.

Audi a4 mass air flow sensor problems