Land Rover Repair: Disco Oxy Sensor, oxygen sensors, universal replacement

Question
I just purchased (4) 4 wire universal replacement oxygen sensors for my 98 Discovery.  Mechanic now says they won't work as the fitted end is too large. Correct?  Do I have to buy the complete sensors (that cost 4x as much!), or can these be adapted?  If I have to buy the complete ones, do I get 4 alike, or 2 "pre catalytic converter" and 2 "after converter?"

Answer
You must use the correct fitting 0/2 sensors. The larger fitting sensors are for a different system, so they are not compatible and cannot be adapted.  There are however, affordable aftermarket sensors that fit this car. You can purchase them from us at www.britisheurotech.com.

It is unlikely that all 4 sensors need changing, but if you were to change them all, the two upstream sensors and the two downstream sensors are the same.