recurring p0420 fault code

[nuddlez4]

I have read the threads on the forum regarding the p0420 fault code and done most of the suggestions

Changed the spark plugs, Put in some proper petrol and give a run, Used cataclean on 1/4 tank petrol and had a blast but the flaming code keeps cropping up
I invested in a OBD reader and when the code crops up I just erase the code and start again The car does not lose power or run rough but the engine light comes on anywhere between 30 and 90 miles which I just reset and carry on
Last week when it came on again merely through frustration I rang the stealers and told them how I had tried to sort out the problem who without inspecting the car advised that it needed a new cat and possibly O2 sensors due to it's age, 2007, and cataclean is a total waste of time
Has anybody got a similar problem and is it a common fault with the N46 2 litre engine

 

[tug]

Yes mate, it is very common on the N46. How do you drive, if you drive economically ie. changing gear as you normally would in say a family saloon then you will see the code more often. I have owned my N46 for 8 years now and is my daily, i found a solution after going through the same as you, early on.

These engines are built to be "thrashed" and if they are not, they dont seem to like it, its as if they get "choked up" :lol:

Best thing i found was to NOT use 95 ron fuel, i always use 99 ron fuel and it helps to a certain extent. But by far the best way to stop the problem is to drive it enthusiastically. ONCE WARMED UP, wherever possible, take it up to at least 4000 revs through the gears, i take mine up to 5000 when i can and very, very rarely get the code. It does however appear every now & then especially when in heavy traffic for long periods, when it does it's always the same code, P0420. I, like you, clear it with a code reader.

If you are going to try out my solution then it would be a good idea to reset the throttle, heres how;

Turn on ignition to full light display but don't start the car. Then immediately count to 15. (1000, 2000 etc) Then immediately turn off, count to 15 in the same fashion then start the engine. This will erase the throttle adaptations & give the Valvetronic a fresh perspective.

You should feel the difference straight away.

Cheers, tug

 

[nuddlez4]

Thanks for the info currently away on holiday ,not in the zed, but will try your method on return and let you know how I get on Many thanks

 

[Z4paul]

All great advice from Tug. I experienced similar issues while in town traffic/driving, followed suggestions on driving style, resetting the throttle...code has come up once in past year then cleared itself after a couple of weeks.
So, definitely try the above and enjoy