My ABS and Brake warning lights both stay on. Also the Speedo doesn't begin to work until after 19mph. Im not sure if they are related. Any ideas what's causing this?

 

It sounds like two seperate things. For the Brake Light check simple stuff (light bulbs, both tail and third light) also check fluid levels and wheel sensors. The speedo problem sonds like a snaped cable or the speed sensor is bad. If it is a bad sensor that might affect the ABS sensor because the computer can't tell how fast the truck is moving.

 

It is most likely the speed sensor in the rear diff.

 

Check the rear wheel speed sensor it's on top of the rear dif.
RWSS is the most likely cause.

 

+1 ... 100% certain this is the problem. Classic combination of symptomsfor a bad RWSS.

 

Thanks for your help. I ordered the part and he said it would be here Wednesday afternoon. My Dodge dealer wanted $55 for it, but my local parts store sold it for $30 with a lifetime warranty. I'll let you know after I replace it.

 

I replaced it last night, everything works. Thanks for your help.