the engine light stays on.

O2 sensors get "lazy" when they get older and MPG's decrease. They usually are good for 80,000-100,000 miles. Replace it to reset the code and increase fuel efficiency.

Your Land Rover won't pass the smog test with a bad 02 sensor. Replacing the sensor should fix the check engine light problem but no guarantees. Have the hoses from the 02 sensor checked for cracks or holes.

Hoses on a O2 sensor? Smog test?

02 sensors are part of the smog system on every car. When the sensor goes bad or a hose goes bad, the car won't pass smog. Quit often the Check Engine Light will go on. The Check Engine light is a "catch all" for many problems.