I recently went to an indoor show where we had to disconnect our negative side to our batteries. About a week after the show I start my car up and suddenly there is a CEL. OBDII scanner says there is an EVAP leak with the code P0455 so I checked if my gas cap was tight and it was. Another weird thing was that the scanner said the battery had low voltage, but the battery health was fine when I checked it right after. A friend told me that since I installed an aftermarket exhaust and removed my secondary cats, unplugging the battery reset my ECU and it "learned" that the secondary cats were missing and the O2 sensors were messing up. Has anybody experienced this?

 

That has nothing to do with the secondary cats missing. It's most likely an exhaust leak before the 02 sensors which is very common especially with the Invidia exhaust. Tighten the bolts where the exhaust connects to the cats and if that doesn't work replace the gaskets with some quality gaskets like this (they also make double thickness but these resolved by CEL). The code reset on it's own after I replaced the front gaskets.
https://www.grimmspeed.com/grimmspee...kaAnLHEALw_wcB
A weak battery can also cause codes and other issues.

 

Weak battery as it causes all sorts of weird system issues. I even got a TVD malfunction warning among others when my OEM Panasonic was on its last leg. I eventually replaced it with the AntiGravity Lithium Ion smart/intelligent battery and never had any CEL issues at all.

 

Probably an exhaust leak as I installed my Apexi exhaust by myself and I just remembered that I forgot to retighten the bolts after driving the specified miles on the manual. I will tighten all of the bolts today and hopefully, the code goes away.

 

Thank you for the input, I will definitely check out that battery as a replacement.

 

The code you got has nothing to do with an exhaust leak. Exhaust leak would trigger cat efficiency emissions codes, usually P0420/P0430. Really wish guys wouldn't send you on a wild goose chase with the initial replies.

A weak/dying battery will cause goofy things to happen. I'd just clear the code and monitor to see if it returns. It may be just an anomaly from disconnecting the battery for a bit, or it could be an issue. If you get any other warning signs of a weak battery, just replace it, don't wait for it to die.

 

Yes 2 days ago I cleared the code and so far the code hasn't come back. I understand the code is not an exhaust leak code but just to make sure I will still tighten the bolts.

 

Sweet, doesn't hurt to check that stuff anyway. Just that some guys see CEL and "new exhaust" in the same paragraph and jump to a conclusion without reading the details. Mainly because leaky gaskets are pretty common.

Just for your awareness, yes most exhausts delete the secondary cat. HOWEVER, the system only monitors the performance of the primary cats, since the secondary cats come AFTER the downstream O2 sensors. So the only way an exhaust will trigger any codes is if there's a leak before the downstream sensors, which on the RCF is the header to mid-pipe connection.

 

True that man.
0455 is the code and small or large evap leak codes do not come from post o2 sensors. Evap leaks can be a nightmare to trace down, the bigger the leak, the easier it is to find. Your first step is to clear the code, see if it comes back at all, and if it does track how long it took to come back. If it comes back right away replace your gas cap first.Aaaand don't cheap out, buy a factory gas cap! Your gas tank has a tiny pump, usually in the vapor/charcoal canister, that pressurizes the system every few hundred miles or so to make sure it can hold pressure. If it does, theres no leak, if it doesn't, then the sensor is bad or there is a leak somewhere. Ive always found the best way to find a leak is to find a few feet of hose, hold one end in your ear and scan around the vacuum hoses. The leak will be amplified like a stethoscope. Hopefully it was just a fluke. Good luck!

 

It's been about 5 days since I cleared the code. I bought a factory gas cap from a lexus dealer and so far it has not come back. So far so good.