My occasionally driven 2007 accord with AT and ~154K miles - yesterday filled up the gas tank and after an hour or so drive, randomly started to throw up CEL.

28-30 or mpg are normal, through manual calculation and no performance issues, clean air filter and fresh fluids.

Scanned it today and it was P0420 code, should I add techron and give it a try?

Or any other inputs and advise? Thank you

 

P0420 is for an inefficient catalytic converter.

Techron won't hurt and may be worth a shot, but probably won't solve that problem.

 

Thanks, any idea if O2 sensors can be cleaned one by one? Does Bank 1 means, downstream sensor? Because I can clean it and see if it fixes CEL and then replace it.

 

Bank 1 & bank 2 are the cylinder banks in a V-6 (or V-anything) engine. Is yours a V6 or a 4-cyl?

Bank-1 Sensor-1 is the upstream sensor, Sensor-2 is the downstream sensor. A 4-cyl doesn't have a bank-2 at all.

I've heard stories about cleaning an O2 sensor using a propane torch, but don't know exactly how and/or whether it actually works.

 

Thanks for the help JB, it's a I4 and autozone scan says P0420 - Bank 1 catalyst system efficiency was below threshold for a predetermined period of time.

It means I should start with the upstream one first then? Thank you

 

No, the catalyst efficiency is measured with the downstream sensor. But even by about 2000 the PCM has been pretty good at recognizing the difference between a bad sensor vs. a bad catalyst. There's other error codes that would point to a bad upstream sensor or even towards a bad downstream sensor.

Have any exhaust leaks? Have any oil leakage around the O2 sensors? The sensors actually measure the oxygen difference between inside vs. outside the sensor. So for example an exhaust leak blowing onto the outside of the sensor will throw off the measurement even when the sensor itself is OK.

 

Thanks, I'll check for exhaust leaks but don't think have any - no oil leaks.

Do you think simply cleaning the downstream sensor would help any? I mean can give it a shot.

 

Maybe so, but I never tried it and I don't know the detailed method.