Error code P0420

Yesterday I noticed that when driving in a 20mph zone the car was really jerky so I tried in 3rd gear and 4th, but both were not running smoothly.

Car accelerates and seems to drive ok at higher revs/speeds.

Upon getting home I checked the FourStroke app and I have the error code "P0420 Catalyst System Efficiency Below Threshold".

Is it worth taking to a garage or are there some things to eliminate before I run to that expense?

Any advice greatly appreciated!

Cheers

Things to look for or inspect are; leaks in the exhaust or intake(post MAF) to throttle-body.

However, typically when you see this code along with power reduction symptoms...there may be a clogged catalyst.

So, you can inspect it for leaks, look at the wiring to both O2's, replace the O2 sensors after you've tested them, or replace the catalyst.

Your exhaust is still stock with the catalyst, yes?

ROH ECHT said:

Your exhaust is still stock with the catalyst, yes?

Click to expand...

Had a new stock cat fitted about 18 months back as the original had rusted through.