Black smoke is escaping from the exhaust, the car has less power and is running in limp home function: These are the possible consequences if the air mass sensor (LMS) is sending incorrect signals. What are the causes? How does an air mass sensor work? What is on-board diagnostics (OBD)? What are possible diagnostic trouble codes? How can you test analogue air mass sensors? You will find answers to these questions and a wealth of additional information on air mass sensors in this article.