Diagnostic code P0420

[John_chafin]

I did a diagnostic on my 2012 civic si sedan today for a check emission light. It ran the code p0420 which with my research seems to be a bad O2 sensor? I'm just making sure this is correct and what my option of fixing it would be. Thanks guys!

 

[Dennis Rockholt]

Did you recently install any sort of exhaust mods?

 

[PMMcivicFB2]

Your only option buy a new o2 sensor.

 

[John_chafin]

Did you recently install any sort of exhaust mods?

Yeah I installed skunk2 alpha series headers, but I've had the skunk2 megapower rr exhaust

 

[John_chafin]

Your only option buy a new o2 sensor.

I figured I was just making sure there wasn't anything else I needed

 

[Dennis Rockholt]

Well you probably damaged one of the 2 sensors during install I'd assume

 

[John_chafin]

Where's the best place to get o2 sensors

 

[Dennis Rockholt]

I'd say the dealer...just because you want em to be good quality.

 

[the insider]

P0420 is catalyst below threshold - usually indicates catalyst is depleted (or missing). The secondary oxygen sensor monitors catalyst performance.

 

[bardley]

That code is a catalyst efficiency below threshold code because the header you just installed has no cat. You can either get it fixed from a tune (which you should get any way) or try spark plug defoulers.

 

[John_chafin]

That code is a catalyst efficiency below threshold code because the header you just installed has no cat. You can either get it fixed from a tune (which you should get any way) or try spark plug defoulers.

I did get it tuned but it came on after I got home from getting it tuned.

 

[bardley]

Did the tuner turn off the 02 sensor do you know?

 

[webby]

^that. Needs turned off in flashpro

 

[John_chafin]

Did the tuner turn off the 02 sensor do you know?

I'm guessing not because it wouldn't be running the code if he did right? I was thinking I just needed a bypass, but I'll call him just to make sure.

 

[John_chafin]

^that. Needs turned off in flashpro

We'll this morning I was driving and when I was down shifting my exhaust got extremely loud and vibrated underneath me, is this one of the symptoms of the o2 sensor not being cut off when he tuned it?

 

[Phroze]

just check it yourself if your settings, should be under sensors or something like that and you might need to have advanced parameters enabled.

 

[webby]

We'll this morning I was driving and when I was down shifting my exhaust got extremely loud and vibrated underneath me, is this one of the symptoms of the o2 sensor not being cut off when he tuned it?

It's doing to make more noise being new. Lots of catless downpipe owners say it changes after some use. Nothing to do with o2

 

[John_chafin]

This doesn't sound like it's setting in though. This sounds like something wrong I'm not sure.

 

[Nix]

Check ya bolts and mounts. Other people have needed a stiffer exhaust mount to keep it from hitting in a couple places.

 

[John_chafin]

Check ya bolts and mounts. Other people have needed a stiffer exhaust mount to keep it from hitting in a couple places.

Will do