detecting a ground wire?

[tipota]

my exhaust fell off, but there was an electrical wire connected to the catalyc converter. im assuming it was just a ground wire? or is the cat connected to the ECU?

[RandomTask]

Generally ground wires connected to the ehaust are braided flat. Does that fit the description? I see no other wire that could be running into the cat...?

[curtis73]

Other than the O2 sensor, I can't imagine any other wire(s) going to the exhaust. If its a ground, it won't have any insulation on it. Either the heat would have melted it, or the factory didn't insulated wire for that reason.

[tipota]

so then the O2 sensor is connected to the cat? because the wire broke on the end and I just wanted to know for when i install the new exhaust. right now my O2 sensor shouldnt be reading anything. how does this effect my engine? i notced that even though there is no exhaust on my car, it does not smell bad at all.

[bjdm151]

If you have purposly removed the exhaust from your car i would suggest getting an 02 simulator just in case. But to really know what is going on we need more information about the car, Specifically what year so we know if it is OBDI, OBDII, or NOBD.

[tipota]

well the exhaust broke and was hanging so i took the whole thing off. I have a 94 nissan sentra, gxe. if it is connected to the O2 sensor, i wanna make sure nothing bad woudl happen to my engine. the wire seems like it was just a ground though, because it looked the same as the ground that came with my cd deck. it had a circle on the end and was fastened underneath a bolt, but i havnt looked closer to see if it actually was connected deeper into the cat. i also looked in my repair manual for the car to see what the wire was, but it didnt mention anything about it in the exhaust section. ill look at the book again, but i did notice how the exhaust does not smell bad anymore, and i heard that if you remove the cat from your exhaust it will always smell bad. im guessing this has to do with incorrect readings of the O2 sensor, and i dont want this to hurt my engine.

[curtis73]

If the other end of the wire is just teminated to a screw into metal, its a ground. Now the question is, why is the exhaust grounded?

You can be assured that it doesn't really need to be grounded, so if that wire truly did come from the exhuast, it can stay unconnected

Yes, the O2 sensors go just ahead of the catalytist, usually in the entry to the catalytic converter. It looks sorta like a spark plug and should have one, two, or three wires coming from it. Not sure how cutting the wires would make the engine run since it depends on whether or not its heated and how the ECU interprets the signal.

But back to the ground... I can't imagine that the exhuast was grounded, so you might start looking for the other end of the wire. Its possible that you have a broken ground wire somewhere else, or its very likely that your O2 sensor used it as a ground.

[tipota]

well if the O2 sensor looks like a spark plug i know where it is. on my car its right below the exhaust manifold, where the heat shield is and can be accessed from the engine bay. once you open the hood its directly in front of you. i figured that ground was just a ground for the electrical system. thanx

[bjdm151]

I know for a fact that nissan does usually put aground from the exhaust to the body. On mine there is a resonator around the middle of the car and it was connected to one of the flenges on that resonator. long story but i had to pull the resonator off to do some work and in all the rust that was there the ground strap didn't make it back on. No problems that i have noticed as of yet. Tipota if you experience any problems post it because i would like to know for my own reference.

[tipota]

the only thing close to an electrical problem is some slight sparking sound coming form behind the panel with the odometer and clock. however, i recently removed and put that panel back, and now the clock wont light up so i dont think i plugged the clock in and i think thats what the problem is. i just wanted to make sure that was a ground and nothing major.