2nd Gen Non-Engine/Transmission No Speedometer Reading

[Native]

I have a 96 2500 4X4. The speedometer was working fine, I stopped at the store to get some groceries when I came out, started it up and took off down the road my speedo was no longer working. I checked the three wire connector on the transfer case, no corrosion, seems to be making a good connection. I have the Dodge service manual for my truck, from what I can get out of the manual the problem has to be isolated to four things, the speed sensor, wiring, the PCM or the speedo. I have not been able to find any diagnostic tests for the sensor in the transfer case. The manual refers to the Powertrain Control Manual for testing. Until now I was not aware that there was another manual? Has anyone had this problem before? Are there any tests I can run for diagnosis? One other thing that is probably important is the odometer and trip meter are also not working and my brake and ABS light come on intermittently although they are not presently on and did not come on when the speedo quit working. Thanks in advance for for any advice.

 

[R-N-R]

Hi Native, Welcome to TDR!



Fill out your signature in the user control panel area with you truck stats so that people will know what you are working on. Most likely you have a speed sensor gone bad, the trick is to figure out which one on a front & rear setup. The most common is the rear sensor located on top of the diff pumpkin. Mine was the drivers side front. If you do a search and can patiently wade through the results, you will find the ohm values for the rear sensor, unfortunately I do not recall what the range is. Also, many people have had good luck pulling it out and cleaning it. Have you been in deep water or mud lately? Also, a few have reported in a wiring problem in the harness between the motor compartment and the sensors. This of course is the hardest problem to find, but you can start by inspecting the harness that runs near the drivers side fender well. Another option is to take it in to the dealer where they can hook up a code reader and tell which sensor it is.



Anyways, what year is your truck? Front and rear ABS or just rear?

 

[Native]

Hi R-N-R,

Thanks for the quick reply, I'll try to get my truck stats set up(I thought they already were). Anyway my truck is 96 2500 4X4 3. 55's NV4500 Rear ABS only

 

[R-N-R]

It is a bit mis leading, if you set up your stats in the truck profile, just copy and paste them into the signature box to show them on your 1st post for each thread.



I am not familiar with the '96, but I would expect that the sensor location is in your manual. On a '96 you might want to find the sensor and trace the wire harness back up to the front, looking for damage along the way. Sorry I can't help more... .



Good luck to ya!

 

[klaybus]

Dead Speedo

On my 99 when the cigar lighter fuse is blown, the speedo stops working. Not sure if it's the same for yours but worth a try.



Clay

 

[DavidC]

Rear speed sensor is about 1800 ohms.



Dave

 

[zstroken]

Speed sensor used for the speedometer on the 96 should be in the transfer case. I could disconnect the one on the rear pumpkin and the speedo still worked. I disconnected the one on the tranfer case and nothing.

 

[vssman]

Yup, It's on the side of the transfer case. It's made up of an 8 pole rotating magnet, 1 hall switch and 2 capacitors. Not much to them. Check all of the connections first and that the gear is actually rotating in the transfer case to drive the VSS unit. There were 2 designs, one with flat blade connectors and one with round. You should have the round one. In order to check it's operation, you really need a 5volt input and an oscilliscope to read the hall switch changing at each magnetic pulse. I don't know what the dealer charges for a new one (but it used to cost less than $4. 00 to DCX when they were made here in the US: read Mexico) - if it's too expensive to buy another new one, then try a salvage yard. They're all the same except for the pin style.

 

[MarkMiller]

rear ABS means you have no front wheel sensors so they aren't your problem. I disconnected the rear ABS and the rear brakes actually work now. I was on the original shoes at 65000mi.

 

[steved]

If it was the rear sensor, the ABS and brake lights would be on.



I agree, pre-97 (IIRC) use just the tcase sensor... most likely it is your culprit.



On the later ones, the ABS sensor runs the speedo to about 30 mph then the tcase one takes over.



steved