i have a 99 dakota 3.9 auto. i have been chasing my tail with the same problem. i replaced o2 sebsors plugs wires cap rotor pcv cleaned throttle. several tmes i cleared these code tried seafoam put clamps on all vac lines etc. i noticed that my neg cable on battery wouldnt seem to really get tight. i loosened it up and found a small screw that i installed, on the batt. post. tightened it down. i used to drive it about 30 miles and the check eng light would come on. i dont know if ths was the fix, but i drove it 70 miles now with no problems

 

Welcome to the forums.

I moved your post into a new thread as the other one was several years old.

Changing your battery terminal, or the cable assembly, might be a good idea for starters.