I was playing around with an aftermarket switch installed in a second-hand truck (2003 Dodge Ram 1500) that I had just bought. I noticed the ABS/BRAKE warning lights come on, and the truck was throwing P0501. After wading through forums here and on other sites I tried just about everything from resetting the computer, to clearing codes, to checking fuses, to checking the speed sensor on the pumpkin. All to no avail.

Symptoms
--------------
ABS/Brake warning light on
CEL on
Reverse Lights not working
Speedometer not working
Odometer not working

Cure
--------
Fuse #3 was fried.

I looked at the fuse multiple times and it looked fine. I must be blind, but after looking at the fuses for the 3rd time in the afternoon sun, I finally noticed it was fried. Here's the link that finally convinced me to re-check my fuses: https://www.justanswer.com/dodge/5ii...no-speedo.html

I'm posting this because it took me hours of searching to come across the fix for my truck, hopefully this will help someone. And hopefully I'll check fuses a little closer next time..

 

Thanks for the update.

 

I know this is an old post, but i thought i may help someone else with the same problem. I was getting the P0501 on a 2004 ram 1500. Speedo was bouncing while truck was just setting idling and ABS light was on. after diagnostics, I found the speed sensor on the diff was damaged along with a bad previous wiring repair on sensor plug. I repaired wiring and replaced sensor. All was fixed