Guys,

Have had my 200 cell from Milltek for about 2 months and the CEL has come on a few times and when reading the OBD codes they are listed as P0420 (Catalyst Efficience Below Threshold Bank1) and P0430 (Catalyst Efficience Below Threshold Bank2). The CEL keeps coming on but can be reset with the OBD scanner.

Would this indicate that the 200 cell cats are not efficient enough or that my O2 sensors have gone bad?

Been thinking of installing O2 sensor bungs to move the O2 sensor away from the exhaust flow and perhaps keep the CEL away.

Any thoughts and experience from the same fault codes is much appreciated.

Ciao, JE

 

What are your fuel trims looking like? Could be the car running rich, and THAT is causing the cats to get 'overloaded' and fail the threshold.

Lots of stuff can cause this code- and NOT just "O2 sensors" or "cats"

 

No idea about fuel supply but suspect it could be running rich as consumprion seems very high. I have not driven the car much since i bought it but it has an ecu flash (spikes at 1.1 bar). Have left it overnight with the battery disconnected so that the ecu will re-learn the basic paramerters.

Thks J

 

I just replaced my exhaust with a SpeedTech w/200 cell cats a couple of weeks ago. I'm getting the same thing. I can clear the codes and they will come back in a day or two. Is there anything short of a flash that can stop this? (If anything, the car should be running leaner with all the extra air going through.)

 

Slider,

Occasionally our 1st generation, 200 cell twin can exhaust causes a CEL on a small percentage of cars. 02 bung extenders usually take care of the problem and they are very inexpensive. Also, these exhausts are getting older now and if the previous owner ran their car too rich or used leaded race fuel the cats could be compromised causing a CEL. PM me if you would like to try a set of bung extenders.