There are apparently two o2 sensors used on a blacktop Zetec.
I believe these are pre-cat and post-cat.
1. Are the two sensors physically the same?
2. What does each sensor do?
3. What is the likely result if the pre-cat sensor is missing/not working?
4. What is the likely result if the post-cat sensor is missing/not working?
The first one is used for the emissions when running in closed loop. This is every thing but tick over and WOT after the engine has reached
temperature.
The second is just to check on the cat.
If you run with out either it will go into limp home mode. You may get away with no cat by adding a resister to the post cat sensor. Google Mil
eliminator mods.
Thanks mate, does that mean on your ECU install on your zetec you have both sensors running? I'm also not running a cat if that makes any
difference.
I only had one connected (with the round green connector) but it's duff so have disconnected for now until the new one arrives, but the car is
definitely not in limp mode!
If the sensor is disconnected the ECU will realise it is faulty and resort to standard mapped settings. It could well run better than if you have a
sensor that is giving crap readings but not as well as when running properly, especially fuel economy.
Ahh, my blacktop is around 1999 i think (from a mk2 mondeo), so i'm assuming i should only have one o2 sensor then.
I'll wait for the new one to arrive and hopefully she'll run a bit better!
I don't have one connected, but was chatting to a guy who "knows loads about zetecs" and told me every blacktop has two O2 sensors.
I wasn't sure so atupidly listened to him...!
