The lambda sensor is also known as the exhaust gas oxygen sensor and is the key sensor in the engine fuel control feedback loop. A computer uses the lambda sensor to balance the fuel-oxygen mixture. The correct reading for fuel mixtures is rich as opposed to lean.
Lambda sensor outputs range from 0.2 volts, which is lean, to 0.8 volts, which is rich. For a perfect balance, which is known as stoichiometric, there must be mixture of 14.7 parts air to 1 part fuel.
The lambda sensor never remains constant, it is always changing. This is known as cross count. The injection system should switch between rich to lean about once per second; if it is lower than this, your sensor needs to be replaced.
A lambda sensor usually lasts between 30,000 and 50,000 miles, but it can stop working sooner if the sensor gets contaminated by lead from an antifreeze leak or if it becomes clogged with carbon. When the lambda sensor starts to fail, the check engine light may come on.
Before replacing your lambda sensor, do a diagnostic check to see what is wrong with your sensor. It could be a simple thing like a wiring problem that doesn't entail replacing the entire sensor.
20th Jan 2015