Vehicle speed sensor 2004 Ram

Trying to logic out a problem in my 2004 Dodge 2500, CTD, 4X4, six speed.
Need to know where the speedometer gets its speed signal?
Where the auto door locks get their speed inf.?
And, where the seat belt chime gets its speed inf.?
If my logic is correct, the speedometer and door locks gets inf. from the same sensor, and the seat belt alarm gets it from a different sensor.
Thanks, Al
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Hey Al, I'm sure Tom or Mike can help you with this better than most but if you like to read, go to http://hemitruckclub.com/ and download the service manual for your truck. It is 80+ Gig though. There is 4-5 pages on the door locks on my '03. It does say that "certain functions and features of the power lock system rely upon resources shared with other electronic modules in the vehicle over the Programmable Communications Interface (PCI) datta bus network." Also, "The instrument cluster will set Diagnostic Trouble Codes (DTC) for the power lock system."
FMB (North Mexico)
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Went through the manual and according to it, Tom's right. The chime is independent of truck motion. But according to my owner's manual and the way the chime worked when I bought the truck, the service manual is wrong. Anyone have an 04 that could check the operation of their seat belt chime and confirm this? Please:) Could this be a 04.5 change? My truck is a 600 CTD.
Al (Southern Arizona)
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The reason for the above was my truck had a wacky seat belt chime.
If anyone is still interested: After two trips to the dealer, both times I was told they could find nothing wrong, it's fixed. The first visit they told me there was nothing wrong and it was working as designed. Took them for a ride, proved it was not working as designed. Left the truck and came back three hours later. Was told they had it all ready to go. So I took it home and it was exactly the way it was when I took them for a ride. Took it back Tuesday, again I was told it was working as designed, but this time it is. They still maintain they didn't do anything:)
After the first visit, the truck had the DRL's on and they disabled the headlamp timer?? They fixed that too. Tried to get them to add the fast idle deal for the CTD. They said it would only work on an automatic truck because it had to have an "in park" signal from the transmission. That's understandable.
Hats off to the service manager Barney at Tucson Dodge. After I talked to him he got right on fixing the problems.
Al
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Probably re-flashed the instrument cluster, correcting some funked-up code that caused some of it's functions to mis-behave.
Ahhh... electronic controls. They're great when the work :)
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The speed signal comes from the ABS controller, which in turn gets rear axle RPM info. from the rear wheel speed sensor. The instrument cluster is programmed with the tire size, and converts RPM to MPH

These functions, which used to be controlled by the Central Timer Module in the 2nd gen trucks, are now controlled by the instrument cluster. Pretty much any and all electronic functions within the cab are handled by the IC.

The IC locks the doors at 15MPH, as determined by the ABS system. The seat belt alarm triggers when the ignition is on, and has nothing to do with motion of the vehicle.
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Checked out the seat belt chime. On my truck if I start it and don't move it, the chime will never go off. Something tells it the truck is moving. My owner's manual says it should start its warning at 5 MPH. Mine used to chime going slow, now it may or may not depending on the alignment of the planets. Wouldn't care except I'm sure it's an indication of a bigger problem. Last Friday the brake and anti-lock warning lamps came on. Dealer says it's normal if you drive on a road with lots of turns. I think it's tied to the seat belt warning problem. They also told me the speed sensor is made up of all three wheel sensors averaged together by the anti-lock brake controller. They say it's like that only on 4X4's, should have mentioned mine's a six speed 4X4 CTD.
Thanks for the reply.
Al
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