Idunno

1996 XJ, 4.0, 230K miles, 2WD - I got this XJ with some rattling going on in my exhaust system from the front pipe back. Today I finally worked on it. I found a loose clamp and tightened it. That solved the lion's share of the clatter but there was still a lot of it audible, yet nothing was loose. I traced it to a bad cat. It had self-destructed inside. I shook it after I got it off and it sounded like the guts had come loose. The innards were probably dancing around inside the shell as the hot gasses shot though it. I removed the aft O2 sensor and set it aside when changing out the new cat and muffler. The cat is a $95.00 Magnaflow. The muffler is a $45.00 OEM equivalent from Advance Auto. When I went to reinstall the sensor I noticed something loose inside the tip. At the very end is a small hole and an internal piece was sticking out if I held it one way, and then it would fall out of the hole when I up-ended it. Is that normal?

Anyway, after getting everything clamped back up I started it. I was like "Oh, so that's what an XJ sounds like." But, my question is does the system throw a code for a bad cat/sensor? I've never had the CEL come on for anything on the truck (so far) but it seems to me if there's a sensor for the cat then the system would alert a failed one.

Thanks.

Idunno

Answering my own question, yesterday I changed the cat & muffler and mentioned what I found with the O2 sensor. Yet, no CEL came on. This morning it did. A quick trip to the parts store for a read-out throws a code for the aft O2 sensor. Ordered a Bosch sensor for about $62.00 and will pick it up tomorrow.