mcolliga

I just bought a '99 sr5 3.4L and the CEL has been on since last November. I was driving down the road one day when it sounded like the muffler dropped off. I looked underneath and the second 02 sensor in the back cat ( has CA emissions) blew out of the converter, I guess the person before me forgot to put nuts on the end of the studs. Well with the rear sensor out the light has gone off. My question is, if I put the sensor back and and just leave it unplugged, will it hurt anything? I live in Louisiana so I don't have to worry about emissions.

mt_goat

The CEL will almost certainly come back, if you unplug it you will probably just get a different CEL. Maybe the reason you were getting a P0420 originally was the exhaust leak around the rear O2 sensor (before it blew completely out).

mt_goat

Here's one way to get around a P0420, but you need the rear sensor in place and working:

http://www.urdusa.com/index.php?cPat...sdc9ev7bcbsch5

Here's another way, without the rear sensor in place:

http://www.vfaq.com/mods/O2bypass.html

I've never done the 2nd way, so not sure how well it works....ie, don't blame me if your truck burns LOL.