The check engine light went on on my 97 Eddie Bauer SOHC recently. I went to Auto Zone to have them do the diagnostic test and it read Error Code PO430 - Catalyst System Efficiency is below limit - Bank No. 2. I called the Ford dealer and they said I might need to replace the catalytic converter or the O2 sensors, but they wouldn't know for sure unless I brought it in and paid $84.50 for another diagnostic test that I already know the reading for!!!. A few weeks ago the same thing happened, and when I went to the dealership I bought the truck from, the mechanic said that running fuel injector cleaner through it for about an hour would do the trick. But they never did it. Was he telling me the truth, or do I really need a new converter or O2 sensors? I'm not to familiar with this type of stuff and I don't want to get ripped off, but I also don't want a temporary solution to a bad problem. (I only have a 30 day warranty and its about to run out!!) Has anyone had a problem like this before? What did you do?

 

You really need to get a proper scan of the system done. More that likely, it is just a bad (or lazy)O2 sensor downstream from the bank 2 catalytic converter, but you need to hook it up and get a dynamic
readout of the sensor transition voltages and times to be sure.
Thats my opinion
Dialtone

 

I had a very similar problem with a check engine light. I was getting code P0420 which is "Catalyst system efficency below threshold (Bank 1)" My mechanic said it was one of the two 02 sensors. Based on the code he thought it was the downstream sensor and changed it but it turned out to be the upstream sensor. So in the end I had to have both changed to eliminate the light coming on. It has not been on since the second sensor was changed. My mechanic is very good and he says sometimes the codes can be vague with the 02 sensors, the dealers won't tell you that however. Be careful listening to dealers because given the chance they will rip you off. He used to work for one so he knows how they operate.

Kevin

 

The downstream O2 sensor is supposed to be "lazy". If it starts getting too many crosscounts that means the cat is not doing it's job and it will set a code.