P0421 on my CP-E Catted downpipe

[steven88]

P0421

Warm Up Catalyst Efficiency Below Threshold (Bank 1)

So I threw a P0421 code on my cp-e catted downpipe...this is actually the 3rd time it has happened now....past few weeks I have been throwing it and I just erase the code with my Equus DTC reader...but it keeps coming back after a few hundred miles

What do you guys think it is? According to the internet, it might be the catalytic converter or the o2 sensor itself

For those who have Cp-e catted downpipe, what would you suggest?

[Crossbow]

Call or Email Cp-e .

[ElBartoRex]

I have been getting the same code for over a year from my TurboXS catless downpipe. Its just your run of the mill cat inefficiency code. It is not uncommon for a cat code to trigger from a high flow cat-- the sensor thinks your stock cat is dying. A spacer will fix it but the spacer trick seems to be hit or miss on this car. The diode will work as well though in my experience the light still comes on every 600-800 miles.

[mike8748]

I have the TurboXS DP, no CATS and I got the O2 extender off eBay:
eBay Motors: o2 oxygen sensor extender 02 EFIE HHO HYDROGEN MAP MAF (item 160328833335 end time May-16-09 1031 PDT)

Over 2k miles and still going w/ no CEL's

[steven88]

Originally Posted by mike8748 I have the TurboXS DP, no CATS and I got the O2 extender off eBay: eBay Motors: o2 oxygen sensor extender 02 EFIE HHO HYDROGEN MAP MAF (item 160328833335 end time May-16-09 1031 PDT) Over 2k miles and still going w/ no CEL's

i thought the TXS already comes with an extender built into the downpipe?

[stormin84]

i get the same code with my catted cp-e downpipe, i know another person with a mazda 3gt with a header and gets the same code too. i just clear it with my dashhawk

[zoomed777]

Try the diode fix, my TXS stealth kit has not thrown any CEL's. I have about 4k miles on it and not 1 CEL yet.

[steven88]

Originally Posted by stormin84 i get the same code with my catted cp-e downpipe, i know another person with a mazda 3gt with a header and gets the same code too. i just clear it with my dashhawk

and it never came back?

[jlefebvre123]

i got turbo xs dp and rp and igot that error once while driving on cruise on the highway for four hours but i just cleared it and moved on

[ElBartoRex]

Originally Posted by steven88 i thought the TXS already comes with an extender built into the downpipe?

it does and it doesn't work (for me)

[steven88]

how often do you guys throw this code? every 1k?

[madvillain]

i get the same, always have. i have the cpe catted downpipe. i clear it with my dashhawk and it stays away for a week or so (100-200 miles.) if i leave it alone, it comes and goes whenever it feels.