Reappearing Fault Codes?!
 

Hi folks,

I got the following 2 fault codes:

P0133 - Powertrain - O2 sensor slow response (Bank 1 Sensor 1)
P0420(!) - Powertrain - Catalyst System Efficiency below threshold (Bank 1)

Had a mechanic replace 'an' O2 sensor (assuming it was the right one..) but the codes are back.


Anyone have a suggestion?
Thanks in advance for any assist - Brgds

If the same codes came back, and they're both targeting the primary O2 sensor, I don't think you can assume the mechanic changed that one.

I had the P0420 code on my car when I first got it. Changed the sensor myself with an aftermarket denso from RockAuto and the code hasnt been back since.

Im worried that its a bigger issue / more complicated than a simple O2 sensor https://www.s2ki.com/s2000/public/st...fault/0028.gif

Another thing the car sometimes does is at WOT around 5.5-7K rpm it will sometimes 'seize' as if it hit the rev limiter.
This is quite unnerving as I drive the s2k on tracks at 9/10ths and such a 'seizure' has the potential to cause loss of traction = bad for everyone.


Ive had the MAF sensor cleaned and that did not resolve it.

Anyone have any ideas/suggestions? HALLLP! TIA

You have an OEM cat or aftermarket? Sounds like ECU and cat recognition issue. Link:

https://www.s2ki.com/s2000/topic/870268-p0420-cel/

No o2 sensor can fix code P420. That is an inefficient cat code, fixed by a new cat or a spark plug spacer on the rear o2.

P0133 you need a new front sensor, or an ecu.

I really appreciate the information folks.

Sounds like I need to have the mechanic replace the 'other' O2 sensor and get an OEM cat (I did get an aftermarket cat).
?

My biggest worry however, is the 'seizing' of the motor on WOT. Would these codes possibly cause that to happen?
I hate worrying that the car may foul my track time.
Thanks again-

It's possible, if the ECU cannot establish proper A/F it may limit WOT operation (lean can fry the engine during WOT so it makes sense)

Sort your codes and get the CEL off first and foremost.

If they replaced the o2 sensor in the CAT it was a mistake, the front one needs replacement.

Yikes, an OEM catalytic converter is like $900 bucks! https://www.s2ki.com/s2000/public/st...efault/089.gif

You have the original one, laying around?

Unfortunately, no. "Wayne" (the mechanic from hell) did not bother to return original parts.