First CEL: P0420 Throwing Cat Code after Y-Pipe Install

So its happened. I purposely asked URD about this prior to purchasing and installing their URD Y-pipe. I'm gonna double check my downstream 02 sensors and the crush washers tonight to make sure everything is sealed tight, but I'm a little bummed.

 

Might have to fake it out.

 

Non foulers? I didn't watch the video but they worked for me on other cars. Be aware though, use a bunch of never seize because they like to stick to the sensor real good.

 

That's the plan. I'm getting 2 x 90 degree offsets.

http://www.bigdaddiesgarage.com/angled-cel-fix.html

 

I've had the URD Ypipe for almost a year now and never threw a code.

Did you just install it? Hopefully when you double check everything it turns out okay.

 

I did install it. I was pretty careful, but I'm gonna check all the fasteners today after work to be sure. So far I've notice better MPGs, but a little bit of a raspy/rattle noise in first gear. I have a hunch that one of the doughnut washers could have slipped when I was torquing everything down.

 

Do you have an aftermarket intake? I noticed that the code popped up when I romped on the throttle to merge onto the highway, so the code was thrown probably at peak emissions levels.

 

I just have a K&N filter and the TRD flow accelerator that attached from intake to the wheel well.

 

Gotcha, I wouldn't think it would make much of a difference, but I was just curious.

 

You must have a bad connection or something. I have the SpecU system with 2 less cats and no CEL.

Also ovtune and TRD intake.

 

Check for exhaust leaks upstream of or near the O2 sensors. An exhaust leak can suck in air as the low pressure tail-end of the exhaust gas pulse passes the leak-making the sensor monitor think the cats are bad because of too much oxygen in the exhaust gasses...

 

This was my fear.

 

When I installed my cat back I took a shop vacuum and wrapped tape around the nozzle. I then plugged it into the tailpipe. I felt for suction in the piping. All clear...no burns. Then I started the engine an felt for hot spots.

My wife I should have used some baby powder in a bowl to see if the powder would have bee sucked up like Scarface. lol

My concern would be baby powder in the exhaust.

 

ive had mine on for couple weeks now and 500 miles later have 0 issues

 

I'm willing to get a sensor or wiring got damaged during installation. I don't think an exhaust leak would cause a secondary cat CEL

 

It is one of the more common causes, though the reason for same is a bit counter-intuitive. The catalytic converters absorb/store oxygen as part of their normal functioning, making the oxygen content of the post-cat gasses low. As stated above lower (than ambient) pressure "tail" of the exhaust gas pulse¹ will draw fresh air into the exhaust system and raise it's oxygen content--the monitoring system expects a lower O2 content and pitches a fit when it doesn't see that....

----------------------------
¹ - the exhaust stream is not a continuous flow,but rather a series of pulses as each cylinder spews it's spent charge. Each pulse has a definitive mass and structure with a higher than ambient pressure "head", a near ambient pressure "body" and a lower than ambient pressure "tail" (it is this lower pressure tail which is exploited in "tuned exhausts" to "scavenge" the cylinder and suck in more new air/fuel charge than plain ol' manifold vacuum would on its own.

 

Well I'll be honest, I was super careful with how I removed the sensors, but then I used anti-seize when mounting them to the URD because they had already corroded/rusted onto the stock y-pipe. Some of the anti-seize got onto the sensors and I had to scrub it off.

Perhaps that caused the sensor(s) to fail?

 

That would do it--click here for more than you probably want to know about PZ O2 sensors...

 

UPDATE: I cleared the code with a scanner after work and it hasn't come back. ¯\_(ツ)_/¯

I'm still going to take a look this weekend and install the foulers. Better safe than sorry.

 

can take up to couple hundred miles for it to come back on