If you have did on-board computer scan and your car is showing error code about NOX sensor probe, it means that your BMW NOx sensor has failed. Xenons4u takes pride to offer BMW 851878901 NOX replacement sensor to replace faulty continental part around UK with 1 year of warranty. This replacement procedure is an easy and pocket friendly option for you which can be done by yourself. There is no need to visit BMW dealer. So, what else you are looking for? Get in touch with us to be sure about part no's and vehicle compatibility list or to place your order, visit our website now!!