i have a 98 type r sti classic impreza. i was replacing the std exhaust last nite and was able to remove the main lambda sensor before the first cat but there was a second sensor after the first cat that wouldnt come out easy and i eventually broke the nut holding it in. can anybody tell me what that is/does and do i need it?

 

any ideas anybody?

 

The o2 sensor is at the top of the downpipe (as you know) the next sensor further back in the system should be a CAT on fire sensor. This sensor puts a warning light up (only) on the dash when the exhaust gas temperature reaches a level that is detrimental to the CAT's health.

So it is safe to remove. Normally I just leave the sensor plugged in and zip tie it up underneath the car (as some cars it'll throw the dash light up if it's unplugged)

 

much appreciated james. i dont think i'll bother getting one for it as its not bringing the light on. thanks again.