Hi there guys. A couple days ago I was driving down the highway and the ABS and brake light came on. Wasn't sure if it was anything big so I pulled over and shut truck off, restarted and lights were off. I asked someone and they said it was common and no big deal. Now, last night both came on, won't go off and now my speedometer wasnt working at low speeds in town but then when I would get to 45mph or so it would jump up and when I would slow down, it would drop to zero again. Is this an issue with the batteries or something bigger or are they separate problems? I have the 99 and no code reader so just trying to figure it out! I did have brakes changed about a month ago and the mechanic said my drivers side battery was weak. I plan on replacing both batteries this morning and hopefully that will help! The batteries are from 07 so it's probably time anyways. Thanks for your help guys!

It would be good to read the codes, but it sounds like a speed sensore issue. probably the rear sensor since it tis messing with your speedo. It is located on top of the rear diff. You might just try cleaning the connections and see if that works, If not, it is easy to replace.

It would be good to read the codes, but it sounds like a speed sensore issue. probably the rear sensor since it tis messing with your speedo. It is located on top of the rear diff. You might just try cleaning the connections and see if that works, If not, it is easy to replace.[/quote

It is fairly easy to do then? Do you pull a cable off and the sensor is there? And that would account for the abs and brake light too?

Thanks

Dripley is right the rear speed sensor is failing that why the speedometer is not functioning properly. Not to mention its messing with the ABS computer because its seeing half a truck rolling faster than the other half so ABS is confused... Just replace the rear speed sensor and you'll be good to go...

Just look on top of the rear diff and its right there. it is a little awkward to get to, but not as bad as a lot of other things.

Right here... http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/23-brake-system/29-antilock-braking-system-abs

It is called a rear differential speed sensor? Is that a Dodge dealership only item? I called my local NAPA and they didn't have a listing for rear differential speed sensor in their computer system. They said I might need to call a Dodge dealer or unless its called something else.Thanks!

Check the connection where the plug connects to the speed sensor on the rear diff. Mine jiggles loose all the time on rough roads. Sometimes it just puts the lights on and sometimes the speedo quits working.

I did drive to another town and got a rear differential speed sensor from a Dodge dealership and changed it in about 20 minutes, mainly because its in an awkward spot, and works great!!! The old one was split apart I imagine from age. Thanks everyone, couldn't have done it without you! Am gonna post a new thread on issue when I took old one out though:(

glad you got it fixed.Just for noted causes, the plug on the ABS computer (driver's side inner fender, btwn battery and firewall) that is closest to the battery, if unplugged, will cause the same symptoms.

Happy you got her fixed.