02 5.9L, please help guys! Went to start the truck and dash lights didn't come on, wouldn't even try to crank. The only light is a flashing red light next to the engine coolant temp. This light flashes constant with key off (and it makes a slight clicking sound from the dash), when key is in on position the light stays solid. No other lights, not even power door locks work. I put my multimeter on the battery terminals and readings were jumping from 8 to 12 volts. I disconnected negative cable, and now battery reads a steady 12.7 volts. Cleaned both cables, reattached and get 8 to 11 volts across battery terminals. Voltage across battery positive to engine ground varies from 4 to 9 volts, my meter kept jumping around with the readings.
I have no after market electrical accessories, I've pulled and used electical contact cleaner on all plugs by the fuse box and the PCM on the other side of engine bay. All connections look good. Last thing I did was changed spark plugs but that was 2 weeks ago. This truck has always ran and started fine. I hope it's not one of the computer components.
Anyone have any other suggestions or questions, thanks for helping!

 

I'm not sure how the '02's work, but maybe your BCM or Cluster is shot?

 

Hey Rich, is there a quick and easy way to test either of those without having to swap out the parts?
I just finished pulling and reseating all the fuses and relays and still no change. I'll probably have to call my shop soon for a tow so they can figure it out.

 

Actually, do you have the security system on your truck?

I do, and that flashing light sounds like my security light on my dash. I wonder if somehow, the computer locked out the whole truck IDK just a guess

 

No, my truck doesn't have the security system, in fact every time I did the IC self test that red light wouldn't even come on (I always thought it was burned out, I had to look in the book today because I thought it was a warning light for overheating LOL).
I had time and did a bunch of searching and it seemed all the other times this problem came up, 75% was solved with just a new battery. I was a bit skeptical because my battery disconnected read 12.8 with a multimeter, but I had no load tester. So I just walked .5 mile in our lovely 100 degree heat and picked up a new battery, dropped it in, wired it up, and already my LED under-hood lights were shining bright. She started right up!
Now I can bring the old battery (just 3 years old) back to advance auto for my core charge, and try and fight them for a warranty refund, even though I don't have my receipt for it now.
Thank you all for your help!

 

https://dodgeforum.com/forum/3rd-gen...-no-start.html

This was the post that convinced me to get a new battery. The OP clearly described the same battery readings just like I had.

Such a great forum

 

Great, Glad you got it fixed easy without a lot of chasing around.

Thaanks for the heads up too about the battery----learn something new