Just wanted to thank all on this thread for helping to resolve recent problems with my 2004 4 runner V-6. Had the CEL VSC and TRAC lights come on a couple of weeks ago. Took it to the dealer and was told that the bank 2 cat was below performance threshold (P0430). Their "good customer" discounted price for the repair would be $960. Went to look for a replacement cat, and NAPA had a OEM replaccment from Walker for $270.00.

Ordered it, but was concerned with the location of the A/F and O2 sensors. Both are located before the part that is listed as the Cat converter, and are just before and behind a chamber that it actually part of the exhaust manifold. I could see no way that the signals from the sensors could tell anything about the part that I was about to replace. Anyway, the new Cat arrived, and I dropped the old part out of the truck, and sure enough, the mysterious that is part of the manifold is actually a first stage Cat, and is a dealer only part.

Returned the 2nd stage Cat to NAPA, and got a OBDII code reader. Sure enough there was only one code in the system, and it was the PO340. Cleared it, and the check engine light went away and has not reoccured, but the VSC and TRAC lights came on every time the vehicle moved. Found this thread and performed the calibration procedure listed above in this thread and now all seems well.

Don't what brought the CEL the first time, but if I had not done the research myself, the dealer would have probably taken me for $960.

Also be aware of the split Cat arrangement. The only section that the sensors monitor is the first section in the manifold. Replacement manifolds are available online from dealers for about $455 vs. the $650 list at the local dealer.

Again - thanks for all of the good posts.