OP
OP
this is how mine look coolant temp 84-87*C at idle
you can see how the post sensor follows the pre sensor more closely than your screen prints.
if you want the 180 second .CSV i can zip it up and post here for you. but it pretty much mirrors the above scren print.
your screen prints suggest that the post cat is attempting to richen your mixture (shown by the low voltage values of the post sensor). and is most likely due to a failing sensor, but could be a cat fault.
my old post cat sensor used to not trace when cold (0.0v), then it would have smaller traces when warm (between 0.0v-0.3v) and when fully upto temp after driving and exhaust gasses were hot it would trace normally(0.1v-0.9v) if i then let it idle and the exhaust temp dropped it would again drop back to tracing between 0.0v and 0.3v. it would seem that yours is doing the same.
i would be looking into putting a new sensor in. buy the best branded sensor you can afford be it Bosch, Denso, NTK or Fiat (which i think are Bosch). i have heard that Bosch aftermarket arent as good as their OEM equivilents but its only hearsay. i fitted NTK and only time will tell if it is upto the job... NTK part number is OZA659-EE31 and Fiat is 46750243 if you want them for cross referencing.
with P0420 you may not necessarily have a Lambda fault code but it may be the lambda at fault. in a nutshel P0420 is set when the ECU thinks that the pre and post cat lambda readings are 'too similar'. this can be caused by a bad lambda but also a physical failure of the cat with good sensors, if that makes sense
ALSO (and sorry for the long post)
check the physical condition of your cat. remove the intermediate pipe and look up into the cat monolith
obviously you need to find the cause of the issue and repair it so it wont happen again (its all too easy to throw bits at a car and not actually fix it) thats the difference between a good mechanic/technician and a 'fitter'
if your sensor has been 'lazy' for a while it can cause monolith damage. as per my previous posts about it here is a a better photo of the monolith damage that can occur with a faulty O2 Sensor.
IF you have monolith damage you will obviously have to replace the cat and i would STRONGLY advise you replace BOTH sensors to stop it happening again.
you can see how the post sensor follows the pre sensor more closely than your screen prints.
if you want the 180 second .CSV i can zip it up and post here for you. but it pretty much mirrors the above scren print.
your screen prints suggest that the post cat is attempting to richen your mixture (shown by the low voltage values of the post sensor). and is most likely due to a failing sensor, but could be a cat fault.
my old post cat sensor used to not trace when cold (0.0v), then it would have smaller traces when warm (between 0.0v-0.3v) and when fully upto temp after driving and exhaust gasses were hot it would trace normally(0.1v-0.9v) if i then let it idle and the exhaust temp dropped it would again drop back to tracing between 0.0v and 0.3v. it would seem that yours is doing the same.
i would be looking into putting a new sensor in. buy the best branded sensor you can afford be it Bosch, Denso, NTK or Fiat (which i think are Bosch). i have heard that Bosch aftermarket arent as good as their OEM equivilents but its only hearsay. i fitted NTK and only time will tell if it is upto the job... NTK part number is OZA659-EE31 and Fiat is 46750243 if you want them for cross referencing.
with P0420 you may not necessarily have a Lambda fault code but it may be the lambda at fault. in a nutshel P0420 is set when the ECU thinks that the pre and post cat lambda readings are 'too similar'. this can be caused by a bad lambda but also a physical failure of the cat with good sensors, if that makes sense
ALSO (and sorry for the long post)
check the physical condition of your cat. remove the intermediate pipe and look up into the cat monolith
obviously you need to find the cause of the issue and repair it so it wont happen again (its all too easy to throw bits at a car and not actually fix it) thats the difference between a good mechanic/technician and a 'fitter'
if your sensor has been 'lazy' for a while it can cause monolith damage. as per my previous posts about it here is a a better photo of the monolith damage that can occur with a faulty O2 Sensor.
IF you have monolith damage you will obviously have to replace the cat and i would STRONGLY advise you replace BOTH sensors to stop it happening again.
