I have an 02 SSEI. The front converter has gone bad. The second converter has the sensor screwed into it. Can I replace the front one with a straight tube without screwing up any sensors or messing with the computer? Any suggestions?

Are you talking about the catalytic converter? You can't legally remove those. If you do you will throw a SES light.

Yes, the catalytic converter. It has two...one right behind the other. The second one in line has a sensor screwed into it. I thought maybe with the first one only removed it wouldn't cause any problems but I don't know. Putting legalities aside, besides making the service engine soon light come on, will it cause any problems?

Thanks.

You have two cats? Hmm, you should have only 1. Let me PM another moderator and see what he has to say.

Is it possible the second one is the resonator?

Well I assume it'* two cats. The first one is small and is right up front where the pipe turns down and starts back. It has a flange on the down pipe that the converter bolts to. The outlet of the converter is welded to a pipe that goes about 1 1/2 to 2 ft. long and is welded to the second converter. The second one looks more like a muffler but it has the sensor screwed into it. Then the pipe goes on back and splits into two mufflers at the very back. Does that make sense? It'* the first converter that is rattling....very bad.

That second one is the resonator. the sensor is the rear O2 sensor. Removing that can be done but can make the exhaust tone become raspy.

You're saying removing the resonator can be done or the converter? If the resonator is removed, what do you do with the o2 sensor?

From the down tube you should have a flex pipe, cat, resonator and mufflers in that order. Pre cat systems were never installed on the Pontiac'* as far as I can tell, but other makes and models have a pre-cat and then the final cat (2004+ Ford trucks are a good example).

It'* sounds like either a heat shield or your flex pipe/down tube might be cracked or bad.

Honestly I don't know what you mean by a "pre-cat" system.
I don't see a flex pipe, just solid exhaust pipe. I've felt around all of the heat shields and everything seems tight. I used a hollow pipe, held it up to the cat and listened and you can very clearly hear a rattle inside like somethings loose.