Will removing my rear two cats cause a CEL?

As the title says, just wondering if I’ll get a CEL from removing the secondary cats. There’s no 02 sensor behind them so I don’t see why it would be an issue, just want to make sure so I don’t gut my cats just to get a CEL.

 

yes they are a monitored system

 

No, only the cats between two 2 sensors will trigger this.

Not sure about california emissions, but I've only seen german cars with secondary cat monitors.

 

The rear cats are unmonitored. Beware you may get extra rasp with the rear cats deleted, similar type of issue the Nissan VQ35 crowd faces.

 

Not to get into a huge argument with people here but yes, most likely will throw a code. Although the monitoring is before and after the front CC the rear cat does have an effect on the downstream o2 sensor. Why it has an effect I can't say for sure, could be back pressure, could be flow rate really I don't know. But what I can say is from experience, removing the rears will most likely hit you with a code. It's hit or miss, might happen might not. I can't remember which code. The adaptors are cheap. You could always just check to see if it throws a code, then order up the adaptors. And come back here to tell us what happened.


Look up O2 adapters.

These work -- http://www.bigdaddiesgarage.com/

 

I've heard that the only time you have issues is if you reassemble incorrectly and have exhaust leaks.

 

No you wont. Ive had an aftermarket y-pipe on for years with no issues. Passed many safety and emissions inspections with no issues

 

Makes sense maybe I had a leak.

After my y pipe install it threw a code. Took like 3-4 weeks before the code came up.

 

Gutted them out and now I’m throwing code p0037.. gonna try those adapters out

 

I've seen the exhaust get disturbed and trigger a p0420/p0430, the donuts like to leak from the manifold flange to the mid pipe after being worked on. I've had 2 year old trucks trigger p0420 because I loosed off the exhaust for work and retorqued it on another spot of the gasket.

Also age has a lot to do with p0420.

Simply the rear cats aren't monitored, it cant trigger the cat codes.

 

Do you think I’d have any luck with getting rid of p0037 if I did new gaskets?

 

Heater circuits is usually just the o2 sensor.

Sometimes we see that from hammer exhaust while the sensor is in place. I've learned to remove o2 sensors before I get violent lol.

Did you change the sensors? Sometimes its as simple as a fuse, HTR CRT something like that.

 

Now that you say that I’m 100% sure I beat the shit out of the 02 sensor when I was gutting the cats. Very dumb
Holy hell they’re $140! You live you learn..

 

Be more cautious than me everyone

 

Atleast it's not a mystery. Report back if the codes disappear

 

Glad you found part of the erroneous, hopefully you’ll have it all fixed up.

 

Sorry for my ignorance but what are you referring to when you say gutted the cat?

 

What’s the purpose of doing this? Clogged?

 

More power baby

 

Ramming a rod thru it (or any other means) to bust out all the catalyst material so its just a straight-through pipe (and is illegal to do at the federal level).
This was something people occasionally did in the early days of cat converters. Today's cats & exhaust systems are free-flowing enough you're not going to see much (if any) power increase (meanwhile with the cats ruined, will cost thousands to replace them should you try to sell the vehicle to someone in a state or county that does emissions testing). Better would've been to just swap the cats for straight piping. That way you can easily put things back after discovering it made little difference.