I've been chasing a CEL issue for quite some time. It will go on and I can check the codes and I get a 300, 301, and 303. I have replaced the O2 sensors more because they appeared weak and not snapping open and closed. My mechanic uses his equipment so I'm not just being the shade tree mechanic. After replacing the sensors last week I set off on a 500 mile journey over several days. I must first state that at no time has the engine ever run rough or stumbled. It has run seemingly flawlessly so I can't point to any symptoms beyond the CEL illuminating. After driving the truck for about 50 miles last week I noticed the light illuminated for a while and then it was off. then I was stuck in stop and go traffic and it started flashing. It flashed for probably 12 times and then stopped. Again, no noticeable symptoms. I drove he truck almost 120 miles further and had the light occasionally illuminate but only briefly. Then near the end of my trip the flashing began again, this time for 20-26 times and again went off. I made my destination and plugged in my reader but all I got was an ERROR message. Trying to clear it I realized I probably cleared the truck too. I left it alone and drove another 100 miles the next day with no events at all. Then yesterday I drove home, another 200 mile trip. Everything was good until I neared my destination when the flashing began again, for another 15 or so flashes. This morning the light was out and I drove a 5 mile trip with no issues. Making the return trip I noticed the light was on steady but this time it stayed illuminated. Plugging in my reader gave me no reading at all. A bad reader, perhaps. I'm going to take it to my mechanic again tomorrow for a reading only to see what he gets.

We did consider a failing computer, but that is purely grasping at straws. I'm done with throwing money at the truck regardless of its low mileage. Even though the new RAM is not the same, it looks like I may be jumping ship.

Does anyone have a reasonable thought or am I floating in the ocean without a life jacket?

And note, a 2001 3.9 with nearly 72K on the clock, original owner and mostly only driver.

 

Continuation of the story.

I threw another CEL yesterday but a steady light without flashes. Tested today at my mechanics and it was the same 300, 301, and 303.

The for sale sign is going up tomorrow! I'm done!