Whats the signs the Catalytic Converter going bad on a 2001 jeep grand Cherokee 4.0

oxygen sensors are always located downstream of exhaust manifold. theres the primary and secondary oxygen sensors. the primary is located before the catalytic converter and the secondary is located after the catalytic converter.

just below the exhaust manifold on the drivers side of the jeep.... u will need to go underneath the jeep an may even have to remove the water shield that is under the front of the jeep..

Your catalytic converter is not doing it's job efficiently enough and it is setting off your sensor. This problem is emissions problem and usually has no effect on the operation of your vehicle( unless the converter clogs) As long as you don't live somewhere they do emissions test you don't really have to worry about it. However if you want to fix it you can take converter off and run a straight pipe or to do it "right" you could go pay way to much to get a new converter put on.

screwed into the exhaust system. one is before the catalytic converter, and one after the catalytic converter. looks about like a spark plug, and have 2 or three wires coming from them.

Sounds like a plugged up catalytic converter to me and the other just sounds like a bad brake light switch

It is screwed to the exhaust manifold.

That's a generic O2 sensor circuit overvoltage warning. Did they find any additional codes? Also, did they clear the code for you? Your car is an OBD2-emissions car, meaning you'll have an O2 sensor before and after each catalytic converter. Is your engine the V8 or the inline 6? If it's the V8, you'll probably have four (although it could be two or three) O2 sensors. If it's the inline 6, you likely only have two. I'm asking about additional codes because that one doesn't help narrow down which sensor is bad. Have you noticed your gas mileage dropping at all? Or a buildup of black carbon soot in the tailpipes? Maybe less power than usual? If so, it's probably a primary (pre-cat) O2 sensor. Those are the ones that determine how much fuel the engine will be fed. If you don't have any discernable difference at all, it's probably a secondary sensor (post-cat). The issue I have is, either of those should throw at least one additional code (either to indicate which sensor is going bad, or in the case of a secondary sensor, you'll usually see a "catalytic converter below threshold" or similar code, since the secondary sensors are used by the computer to see how well the cats are working).

Any additional codes in there, or symptoms you can describe?

tinyp78 has it right if it has the check engine light on then don't run it as it will damage the catalytic converter, as well if the injector fails and exlodes the parts can go into engine and damage a valve or cylinder.

Definite symptoms of a bad catalytic converter. A smelly exhaust and loss of power are early signs of catalytic converter problems. You may notice increased heat on the floor boards as well, When the converter goes bad, it heats up. Hope this answers your question. All the best!
Greg

loss of power can happen even if exhaust does not flow in other words you have a rstriction in the exhaust usualy the catalytic converter has collapsed any exhaust shop will be able to tell you right away, or when you loose power do you hear a hissing noise ? if so that is clearly a clogged converter replace the catalytic converter