348 Error codes 4121 and 1212

Hi guys,

I'm getting these codes on both sides on my 348:

4121 - Catalyzer temp ECU
1212 - Lambda regulation multiplicative value for self adaptation

Sometimes my 1/4 or 5/8 come on and then go off quickly. Other time they stay on one at a time or both for a while and eventually go off or until I do a reset. The car runs fine, no slow down lights or banks cutting out. I was getting a rough idle when the car was cold at first but that seems a lot better now since the car is getting used more regularly.

I have ordered a couple of new 02 sensors to try but any other ideas? Obviously can't do the usual swap to isolate the issue as it is on both sides.

Thanks!

 

Forgot to mention I have tried disconnecting the cat ecu, doing a reset but still get the 4121 ans 1212 codes.