Rattling sound at idle with P0430

[goldenwarrior1]

Thought I would share this with the forum in the off chance someone else may experience the same problem. A few months ago I began getting random P0430 codes combined with a rattling sound at idle on my 02 C4S. The rattling noise varied and at times would completely disappear with no discernable pattern or frequency. Sometimes the P code would pop in 15-20 miles and at other times it would go for 100-150 miles before popping. I suspected the ceramic inside one of the cats had broken loose but didn’t want to pull the cats until I had a replacement to verify. I monitored the system with my Durametric software and I definitely had low efficiency on Bank 2. So, with the cost of a new cat at over $1200.00 I patiently began searching for a low mileage cat.

I found a great deal on a complete exhaust system from a 05 C4S that the owner had pulled with less than 1K miles to install an aftermarket system. I replaced everything this past weekend and both the code and the rattle are gone. When I shake the bank 2 cat you can hear the ceramic insert moving around. I haven’t driven the car enough to see if the code returns but based on what I found I am very confident the problem is resolved. Thanks to Loren for all the help and info during the process.

:renntech: