I have a 2012 Ford fiesta and about a week or so ago my check engine light came on, the next day I went and had someone run to see what code it was and the only code that came up was P0420, I know that means that the cat isn’t working efficiently. The guy told me he would turn it off to see if it would come back because he agreed that the car was seeming to run just fine to see if that was the actual problem and today it did. my car is driving completely normal and I haven’t noticed a single issue with it. I haven’t had someone run it again for a code but I have a feeling that’s what it’ll show. I don’t really wanna pour money into this car either. Since I know it’s running fine is it okay for me to just drive it?
Edit: also forgot to mention the light came on after I filled up my tank from almost empty
Okay, so I actually have a fix for this. Mine had the same issue. When you fill up, do you let the pump click off when it hits full, or do you estimate how much you need and stop before it clicks?
The reason I ask is because this problem happens if you let it click off. It’s actually really easy to fix, and I’d recommend going to a Ford dealer to buy the part—it’s cheaper there. That part was causing the code for me, and I went through the trouble of replacing the fuel cap thinking that was the issue. Turns out, it was this instead.
Second this and it’s such a easy part to fix, it’s in front of the engine, just need clamps or pliers to remove the hose clamp, a pick tool to get the hose off, two screws hold it on and it just needs hand right, no need to torque check.
I’ve had that issue for over a year with my 2011 Fiesta and haven’t had any problems. I talked to a mechanic with over 40 years of experience, and he said not to worry about it.
If it runs fine, just replace the O2 sensor. If that doesn’t fix it, consider using a defouler. It’s an extension for the post-cat O2 sensor that tricks the computer into thinking the catalytic converter is within the efficiency range. You can get both parts and an O2 sensor socket for around $25-30 if you order online.
Is it easy to change the o2 sensor? I don’t have really any experience on working on my car and don’t wanna mess anything up. Luckily I just got smog done so I’m good for a bit haha
It’s literally just screwed in to the exhaust and one plug you unclip. Just need a socket wrench, and 02 sensor socket. It’s pretty open and easy to reach. Just look behind the engine, and you should see them. Youtube will be your best bet of seeing someone do it.