Speedo/abs/no bus problems
 

I've got a 99 dodge ram 2500 that I picked up. Used and well abused. Runs/shifts good.


When key is turned on speedo jumps to 12mph and stays there. 15 seconds in the no bus message appears in odometer. All other gauges work. I did a little research and some basic checks.


ABS sensor in diff was good but there was an open circuit back to the connector below the drivers wheel well. Fixed the wiring and now get a 2000 Ohm reading at the connector.


I am trying to figure out what the PO did. There does appear to be some new wires. I have shown in the pic. Not sure where they came from or where they go. Also there is a 4 wire connector that is not connected to anything. Any help or ideas? pic showing the re-wired relay and unplugged connector



http://s1235.photobucket.com/user/thejimmooney/media/P7270302.jpg.html

Hello,
2K ohm sounds about right reading through the wiring run because your reading through the Anti-lock controller internal circuits.

Attachment 30375


The ABS problem may also be a loose connection at the ECM/PCM on the left side of the block.
Or at the ABS controller. The white and orange wire is the Vehicle speed sense in from the ABS controller to the ECM/PCM.

Does the truck have an aftermarket fuel pump? like a fass or Airdog.
The relay tie wrapped to the line looks like the fuel heater relay.
let me know the colors of the wires at that loose plug and i will see if i can find it.

Thank you for your response and attempt to help. The four wire connector that is not plugged in is the 4 wheel ABS connector according to the service manual I could track down. It's not plugged in because I do not have the front abs sensors. I assume harnesses were the same.


More on the relay. It is plugged into a 4 wire plug. One is 20 gauge red wire that goes to the ground side of the fuse box and has a 15 a fuse inline. Second wires is 20 gauge green/black that goes back to a connector behind the drivers wheel well. (there are two connectors there. one has the rear abs speed sensor and the other connector is where this green/black goes but I cannot find this connector in the manual). The other two wires are yellow/white and black/white which go to a connector that has two black wires to another connector which goes back into a harness on the back of the engine.


Any thoughts?

Any Updates?

The only wires I can find that are yellow/white and Blk/Wht is on the fuel transfer pump ( on the second attachment ) two wire plug.
I think if you see a red wire with a fuse on it that would be a power wire. The ASD relay has a Grn/blk wire but the other colors don't match.

Attachment 30401

Attachment 30402

Attachment 30403

The yellow/white and black/white wires just happen to be there on the terminal side for the relay. I do not think those colors are correct. looks like two black wires but really hard to tell and get to from either the hood or underbelly. maybe I'll try some camera shots to see better.


Thinking about changing tactics as well. since the speedo reads roughly 12mph. It must be getting some signal? I assume voltage? Trying to traced that wire or signal from beginning to end. It starts at wheel speed sensor at diff red/violet orange/violet twisted pair travels up frame rail to C129 then input to the CAB. Out the CAB as orange/white wire to PCM. Where next (ECM)? What color? What are the chances of a bad CAB? causing all of this now?

Best I can tell is it is yellow/white and black/white going into the harness that continues on to/from the PCM. I did disconnect the relay and it still started but took a little longer.


I disconnect the CAB connector and the brake light went off but abs still on and speedo stayed at 12 mph.


I did find another loose 2 wire connector. gray connector looked like red/gray? and red wires. Connector attached to pdc side but nothing from there.

If you unplug your speed sensor in the rear differential does the speed drop to zero?
I am pretty sure that 1999 had ABS front and rear sensors at least my 2wd does.

I would say no it stays the same on the rear sensor because it was an open circuit when I started this process. I'm not sure about the all wheel abs. The red/gray red connector is the left front wheel speed sensor but it has a blank plug as is shown in the service manual with rear only abs/ I didn't see any sensors when I got underneath but not sure where they would be either. I will try to cipher the service manual.


My thinking says at this point to work my way from the speedo back. But I'm not sure what wire/connector controls the speedo

It looks to me like a white/Blk wire runs the speedo at pin 9 on the cluster. It comes from the ABS controller through joint connector #7.The controller is fed from the ECM/PCM.

Attachment 30409

Attachment 30410

Here is the ABS schematic if i didn't send it before.


Attachment 30411

Thanks again. Still working through it as I have time. I did the instrument cluster test by depressing the odometer/trip odometer. I'm not sure it made it all the way through before it faulted out. It acts like the zero point for the speedo is set at 12 mph but it did cycle the needle as the tach cycled as well.


I'm not sure that this tells me anything but I took the instrument cluster out of my 98 1500 and swapped into the 99 diesel. Speedo stayed at zero. abs and check engine light stayed on as well. Bright headlight indicator stayed on....


I'm gonna try to run the codes this weekend to help with the diagnostics