I've never heard of any HR codes, only P####
codes. I have the same truck '04 Ram 1500 5.7L
Hemi. The highest # code on that truck is P1899 so
even a P5221 does not exist. Don't assume that
AutoZone (or any other parts stores) employees are
mechanics or even know what they're talking about.
I've talked to 100's that probably couldn't spell their
1st name. If it was an O2 sensor it would be 1 of
these 3 codes P1195, P1196, P1197.. If it really was
an O2 sensor issue, and a decent mechanic took
care of it, then you may just need to reset your
check engine light (ecm computer). Really easy to
do yourself. Just look it up on YouTube. I would
come and do it myself, as gorgeous as you are
Jasmin, on 1 condition.. Let me buy you a beer!
(Can't blame me, guess I might as well try!) Anyway
good luck and hang on to that truck, I got 358,000
miles on mine and still runs like a champ! A couple
friends of mine got the dodge Hemi's too.. They last
forever! Jeff