My last smog test just slipped through the cracks. The check engine light is on now. This code is popping up: P0420; catalyst system efficiency below threshold. My car is a 99 ej8. Where should I buy a cat besides a junk yard or ebay. Thanks

 

Advance auto has them for like 75

 

buy a universal cat & weld it

 

Before buying a cat, make sure the code isn't caused by an exhaust leak.

 

true.. and also that 99 is OBD2, so could his secondary O2 sensor (the after cat O2) be throwing this code by mistake???

I'm not sure as my civic is OBD1, but I know on my 99 Silverado I was getting "catalyst system efficiency below threshold" and thought I needed new cats and read on a Chevy forum that sometimes the rear O2'a are going bad trip that code and to replace them first.. which I did as it was way cheaper and it fixed my problems, months later still no codes. Perhaps some other people will chime in and let you know for sure.

 

If they don't actually test the emissions, do the spark plug non fouler trick, or buy a 02 sensor thingy to trick the ECU into thinking it works.

 

Unless a CEL code for the secondary O2 sensor is also thrown, the cat code is caused by either an exhaust leak or a bad cat.

 

Gotcha, good to know.