I am having some troubles with my 2001 Neon ES (SOHC). It came up with a check engine light, so I took it to Advance Auto and they ran the code and it came up with "Catalyst Efficiency Below Threshold". The Dodge dealership we bought the car from said it was the O2 sensors giving out, so we spent $180 to change both with Bosch sensors, and it's still coming up with the same code. I think that the code might be signaling that the Catalytic Converter is plugged up and not flowing enough for emissions standards...

Any ideas??

 

Yes the code could be correct and O2 sensor could have been just fine. So now replace the cat but find out why it failed. They just don't normally fail. They are ruined somehow 99% othe time.