So i have a 2003 s2000 with just over 170,000 miles on it and now i have a cel saying that the is a problem with "cat efficiency." The cat is still the original one and Im thinking its time to replace it. Am i right?
Also, i just installed a new post cat o2 sensor.

and also, how would i test to see if the cat is failing? is there any way to do it using the OBD2 data?

 

you can use the primary and secondary 02 data if you have a good enough scanner to tell you that info.

if your primary and secondary 02 readings are close, then the cat is bad. if the readings are around 1/2 a volt or so difference, then the cat should be good.


@170,000 miles id say its time for a cat lol... mine went at 115,000 in my 03.

get a test pipe with a CEL fix though

 

yeah ill do that test, thanks.
And i cant get test pipe because this is actually my girlfriend's father's car and he is trying to pass the SMOG.
i reset the CEL after replacing o2 sensor and it stayed off for like 40 minutes. He went to the smog test place and he passed the emissions but failed the MIL/Check Engine Light self tests. The reason for that is because i just reset the cel and deleted all the self tests.
Then after failing the SMOG, he got a CEL again. And again, it was the Cat efficiency error. Can he pass the SMOG if his CEL for the cat efficiency is on or will I have to get him a new cat?