Speedometer question

[Boonieman]

Do any of you know where the pickup sensor for the speedometer is located? My truck has 28,000 miles and the speedometer is acting up. At highway speeds it wil intermittently start bouncing around all over the place. It will also do it at a dead stop while sitting at a light or something. I don't notice anything with the engine at highway speeds, but at idle when the speedo starts acting up, it sends the engine into a surge. I'm surge the false speedo reading is confusing the the computer. Plus, at highway speeds I sure wouldn't want to be using the cruise when this happens. I'm going to take it to the dealer for sure, but I was going to just check for a loose wire or something but can't figure out where the speedo is getting it's signal from. The other thing I've noticed recently is the 4X4 light is coming off and on at times when it''s not in 4X4, and then won't come on at times when it IS in 4X4. Not sure if the two could be related or not, like a common wiring harness, etc. I didn't know if anybody else had experienced anything similar. This is my first problem with the truck, so I'm not complaining... . yet.

 

[Boonieman]

Here's another question... I looked on line for parts listing and I did find out that it's called a vehicle speed sensor. According to what I read, the sensor for the 48RE auto is about $36. For the manual transmission, it's listed $579. Surely they jest... . ???

 

[XJSuperman]

When they recalibrate your speedo if you change tire sizes they go into the ABS (antilock brake system) to do so. That may be somewhere to look for a problem.

 

[RankRam]

On my 99 the speed sensor was on the rearend, upper right of the pumpkin.



Take a look and you should find it, I don't think the 03's American axle could be much different.

 

[sag2]

Sounds like you might have some electrical noise going on. Be sure to check the PCM connectors for water/corrosion. I saw one that was acting crazy and we just twisted a new pair of wires from the speed sensor on the trans to the pcm. It was picking up voltage spikes.

 

[Boonieman]

Thanks for the tips. I did crawl under the truck before I came to work tonight and there is a sensor on top of the pumpkin of the back axle, and I'm assuming this is the speed sensor. I traced the wiring harness under the bed up right behind the front driver tire. There are two large electrical connectors there and they've obviously been exposed to quite a bit of mud, water, etc. I'm tempted to disconnect and clean them and them tape them up real good to seal them. But, with the truck still under warranty, and the sensitivity of modern electronics I guess I'll just take it to the dealer. I never have gotten any of the reflashes they sent me notices on anyway, so I guess they'll do that too. I was really reluctant to let them do it because the truck has been running so good and I haven't had any problems with it.

 

[Kerm]

How do you recailbrate your speedo? Dose someone sell a unit for our trucks?

 

[XJSuperman]

To recalibrate you need to know how many revolutions per mile your tires make. Your tire manufacturer will know this.



Then go to the dealer (and you'll probably get raped but you gotta do it) and tell them you put on larger tires and have them recalibrate it to the correct revs per mile. Depending on how bad your dealer is you'll pay between $30 and $80.

It has to be done this way as it is done via the computer in the ABS program.

It should take them about 15 minutes (from when they start)

 

[NSperduto]

Originally posted by RankRam

On my 99 the speed sensor was on the rearend, upper right of the pumpkin.



Take a look and you should find it, I don't think the 03's American axle could be much different.

Isn't that the speed sensor that has to do with the ABS, not the speedometer ? I thought they were different things.

 

[dunderkofler]

Hate to bring this back from the dead but my truck just started doing the same thing. I found it somewhat amusing the first time - pegged the speedometer while stopped at a red light, idling in neutral. Annoying while driving now that it causes the cruise control to kick off. What was the solution Boonieman?



Dale

 

[Boonieman]

Mine was the wiring harness connector, according to the tech. He told me he unplugged it and reseated it, but then when he wiggled it, it would make the speedo jump... . so he replaced the harness. I didn't actually crawl under to verify it, but that's what the repair report said. Mine started off doing in just a little, then got progressively worse. They fixed it under the 36,000 warrantee. Hopefully you're still under that. I barely made it. Good luck.

 

[Boonieman]

I'm speaking of the wiring harness under the dash, I believe they referred to it as the instrument cluster harness if I remember right.

 

[dunderkofler]

I'm speaking of the wiring harness under the dash, I believe they referred to it as the instrument cluster harness if I remember right.

Under the dash... didn't even think of that one. I disconnected, cleaned and coated with dielectric grease the connections under the truck but the ones in the cab never even crossed my mind. I guess it's time to go wiggle some more wires. I've got 53,000 miles now - but since it was the first year of the HPCR in the Ram I also bought the extended warranty. Thank you for giving me another place to look.



Dale