durham4416 Posted April 2, 2012 Report Share Posted April 2, 2012 my brother in law has a 2002 325i and since he bought it about 2 months ago the emissions light has come on a few times then gone off on its own, i plugged it into my laptop and read the fault codes using inpa, there were 4 faults relating to lambda probe, anyway i cleared the faults and took it for a drive, the only fault to come back was; lambda probe downstream sensor 2, am i right in thinking this will just be a case of fitting a new lambda sensor, also which one will it be as when i had a 330 i remeber having to replace one and am i right in thinking there is a post cat and pre cat sensor as im pretty sure you can tell which sensor by different symptoms, cheers in advance Quote Link to comment Share on other sites More sharing options...
Jay. Posted April 2, 2012 Report Share Posted April 2, 2012 As it says downstream sensor 2 would that nnot mean post cat as I'd imagine sensor one is pre cat? Quote Link to comment Share on other sites More sharing options...
durham4416 Posted April 2, 2012 Author Report Share Posted April 2, 2012 Cheers jay Anyone know for deffinite? Quote Link to comment Share on other sites More sharing options...
DJ Syxx Posted April 2, 2012 Report Share Posted April 2, 2012 "Downstream" is post cat and "upstream" pre cat AFAIK. Quote Link to comment Share on other sites More sharing options...
durham4416 Posted April 3, 2012 Author Report Share Posted April 3, 2012 Thankyou, will this be causing poor mpg? Quote Link to comment Share on other sites More sharing options...
Jay. Posted April 3, 2012 Report Share Posted April 3, 2012 Yes, I had the post cat lambada sensory changed on my 330 & it went better on fuel Quote Link to comment Share on other sites More sharing options...
CompDoc Posted April 4, 2012 Report Share Posted April 4, 2012 Downstream sensor 2 is the one under the car on the rear manifold. It shouldn't make any differance to the MPG as its only there to check that the CAT is working OK. The ECU only changes fueling on information from the pre-cat sensors. (The ones on top of the exhaust manifold). Quote Link to comment Share on other sites More sharing options...
