I have been trying to fix this problem for awhile now. 2004 Ram 2500 4x4 with a 5.7 Hemi. The Engine light is always on. Before I did anything I fixed the exhaust leak which had the manifold bolts that were broken. That did not help, the light stayed on. I then had it scanned, I don't have a scanner. Ok it said O2 left bank / upstream. I replace both upstream sensors the light goes out for about ten minutes then back on. It is on for good again. I had replaced all sensors about 5 years ago also. What to do?
Bob