Fault code p0420 - please read thread need help !!!!!!!!!!!!

[richard parsons]

Hi Guys.

I have a clio sport 172 - car keeps throwing the above fault code - catalyst efficiency below threshold bank 1.

I have a custom stainless exhaust from the cat back and a 600 cell highflow sports cat fitted, charlie at prospeed stated the clio's are notorious with decat or highflow cats to throw management lights on and told me when i had the car remapped to ask them to include it with a decat program into the ecu which i did but it still keeps throwing that bloody fault code.

can any one shed some light on this and can any one tell me if its the front or rear lambda that is causing the problem ???

Cheers all and thanks

 

[bashracing]

you need to do a live read of the data, but normally cat efficiency below requirement means exactly that,

 

[richard parsons]

cheers bash !!
My mate is dropping his s**t hot code reader off for me tomorrow afternoon so will come back to you with the live data from the car.
If it is the cat the good news is it is under lifetime guarantee and they will change it free of charge.

 

[Shocker]

Cat efficiency code means it's the difference between the pre cat sensor and the post sensor
The second sensor has to see a lower redding than the first , if the second sensor reads higher than first a certain number of times it throws up that dtc
You either have a faulty cat or not as efficient as seller says
But probably the map is wrong and the numbers are to close together
Toyota rav 4 is well known for this even when on Good cat it's just the numbers Toyota use to monitor cats efficiency is set to close together