CEL wen't on a couple of weeks ago and finally ordered one of those bluetooth ELM327 readers from amazon.com and installed the Torque app on my phone.

It's giving me the p0420 fault code, catalyst efficiency below threshold bank 1.

what things can I look at that could cause this code besides bad cat that are specific to x300?


135,000mi, runs fine. Fuel mileage might be a little on the low side. Averaging 15-17 mpg per tank.

 

Air leak, engine inlet (such as leaky intake manifold gasket). Air leak, exhaust (cracked exhaust manifold is common). Lazy oxygen sensor. Faulty catalytic converter.

Do you have freeze fame data? If so, is your LTFT at "100" whenever the code sets?

Cheers
DD

 

A scantool won't be much help on the X300 to assess the catalysts. These are much different O2 sensors than other cars; how they measure catalyst efficiency can't be "watched" like it can for later cars. They use an "area difference" method that can't be "seen", it has to be calculated by the ECM.

You're best bet is to make sure all unmetered air leaks and EXHAUST SYSTEM air leaks are eliminated. Take the shield off the exhaust manifolds and check them good for cracks and gasket leaks to the cylinder head. Check all the welds on the downpipes and cats. If you are confident all is good there, and the P0420 repeats a time or two, you can assume the catalyst is in fact failing. That would not be hard to believe at your cars age and mileage.

Good luck!

 

"LTFT"? Long-Term Fuel Trim?

I reset the light and driven nearly 100 mi since without it returning. I can access freeze frame data, but not sure when I'm supposed to look at it...

xjrguy, I will inspect the car to the best of my ability for air leaks.