Land Rover Repair: Check Engine Light On - O2 Sensor Fault Code, land rover specialist, o2 sensors

Question
Recently purchased a '97 Disco with 180K miles.  Vehicle has a history of failed emissions test (almost every 2 years).  Cat converter and all O2 sensors replaced at least once by previous owner and I had same replaced after purchase.  I also had replaced battery, alternator, spark plugs and wires, and fuel filter and check engine light came and has stayed on saying there is a fault with the lower O2 sensors.  Longevity of the problem suggests must be something other than the cat and O2 sensors.  What else could be causing this problem?  Since problem has been long-running and engine still works, is that an indication okay to keep driving with check engine light on?

Answer
If you guess and replace parts, it's going to be very expensive.  There are hundreds of reasons why your vehicle might fail emissions.  There is no reason to think any of the parts you list are (or are not) implicated in the current failure.

Since we don't know what the failure is, there is no way to know if it's safe to drive.  What I do know, is that ignoring the light means you have taken away your only warning mechanism if an ADDITIONAL engine problem crops up.  Maybe this problem won't kill your motor, but other problems will.  If one of those dangerous problems occurs next week while you are choosing to ignore the light, you could pay a high price.

I suggest you find a qualified Land Rover specialist (not a generalist repair shop or a parts store guy with a code reader) and see what's actually going on, and what's needed to make it right.