What was the code?

There are actually 2 on each side, but the catalyst for the bank 1 side is routed over to the bank 2 side before it heads into the muffler.

Just keep in mind there are a total of 4 HO2S on this vehicle (unless it happens to be one of the few v-8s with 3), one bank 1 pre-catalyst, one bank 1 post-catalyst, one bank 2 pre-catalyst and one bank 2 post-catalyst.

Very often you'll get an HO2S heater code. If this is the case, I'd get a schematic and find out if there is a good power supply and ground to each of the 4 HO2S. If there is and they're all original, I strongly advise you to replace all of them. The heaters degrade with age, and the first one to set a code is usually just the first, if you know what I mean.

Remember to use plenty of penetrating oil, and it wouldn't hurt to pressure wash the sensors before you replace them.

Please post back and let me know how it goes.