No speedometer and abs

[fmj]

On way home yesterday abs and break lite came on. Speedometer went to zero. Have PacBreak and Ats commander which didn't work. I finally got an engine light which gave me a P0500 and P0501 (vehicle speed not detected). Would explain why no lock up as Ats commander is set for 32 mph and no lockup no exhaust break. Seems easy to fix but confusion entered the picture. There are two "speed" sensors. One goes in auto transmission, the other is and abs wheel speed sensor. Not sure where it goes as service manual shown a sensor in front hub (4x4) and there are no wires that I see on my truck. Questions are, how to test or determine which sensor is needed, and where does the abs wheel sensor go? Any clarification appreciated

Here is info on truck: 2001, 2500, 4x4, pacbreak, ats trans with commander, auto trans.

 

[DavidC]

No speedo tells me the differential sensor on the top of the pumpkin which can also give you the other lights. Unplug and use an ohmmeter across the sensor two pins. A good sensor if I remember right is around 600 ohms. When bad they usually read open.

Dave

 

[fmj]

No speedo tells me the differential sensor on the top of the pumpkin which can also give you the other lights. Unplug and use an ohmmeter across the sensor two pins. A good sensor if I remember right is around 600 ohms. When bad they usually read open.

Dave

Thanks Dave, will ohm it out tomorrow. Will post results.

 

[DavidC]

Just checked, memory not so good. 600 for wheel sensors, 1800 for differential.
Third post down
https://www.turbodieselregister.com/threads/abs-light.246522/#post-2379070

Dave

 

[fest3er]

Wasn't the '97 the last year they used the trans for speedometer? At least '98 forward they used only the rear diff sensor for ABS and VSS.

After enough years, the sensor leads can flex too many times and break.

Also the CAB (Controller, Antilock Brake) electronic unit under the hood can fail, causing at least a few similar symnptoms.

 

[KATOOM]

Pull the tone ring sensor out of the top of the differential and clean it off. Its likely full of metal dust and causing signal interference.

 

[DavidC]

Wasn't the '97 the last year they used the trans for speedometer? At least '98 forward they used only the rear diff sensor for ABS and VSS.

After enough years, the sensor leads can flex too many times and break.

Also the CAB (Controller, Antilock Brake) electronic unit under the hood can fail, causing at least a few similar symnptoms.

On my 99 it does have the trans. speed sensor and I believe is used for some trans. operation not the speedo. I was under the truck one day and decided to check it and it read open. Went to the parts store to get a replacement and checked it read around 600 ohms. I pulled the original put in the replacement and never noticed any difference. Maybe with the DTT and Smart Controller it did not care ?.

Dave

 

[fmj]

Well got under the truck an checked the sensor. As DavidC mentioned it was bad. Ohm showed completely open. Installed a new one today. Bad news is still no spedeo. Get voltage to wiring going into sensor??? Cleared codes before I took it out for a drive and no codes yet.

 

[DavidC]

Check the wiring from the axle to the frame. That is a flex point and reports of problems in that area. You may have to resort to ohming the wiring from the front to the back as the insulation may be ok but the conductor broken under the insulation. You may be able to find it in that area by lightly tugging on the wire between your hands, if the conductor is good no stretch, if broken under insulation there will be some stretch of the insulation.


Dave

 

[DavidC]

This is compliments of Katoom, he posted a 01 manual and I picked it up. Do you have a service manual ?. Make sure these two fuses are good.

 

[KATOOM]

This is compliments of Katoom, he posted a 01 manual and I picked it up. Do you have a service manual ?. Make sure these two fuses are good.

Thanks for the appreciation.

 

[DavidC]

Thanks for the appreciation.

You deserve the credit as you help quite a few others with their problems .

Dave

 

[fmj]

Thanks again. Was wondering about fuses if there were any. I have service manual and was going to get to wiring diagram today. Also checking part number for new part just to make sure its the right one. Got it from O Reilys and its a ABS314. Looked for any marking on old one but there are none. Will keep working this as have trip scheduled next week towing 5er.

 

[DavidC]

Although not an absolute did you ohm it before installing ?. Somewhere around 1800 ?

Dave

 

[fmj]

Yes I ohm it before I installed. Closer to 2000. Just got out from under truck. Pulled sensor again to make sure it was clean. Checked the fuse in junction and power box. They were good. I get continuity between pins on harness, and wiggled end by sensor to make sure it didn't fall off. Checked the harness from back to front for any fraying of damage (that was fun). All looked ok. Question is should I get continuity from harness pins to ground?? When I check from pins at sensor end and to frame I get continuity. Are there any inline fuses besides the junction box and power box?

 

[DavidC]

No more fuses that I know of.To check harness from front to back
1. Unplug both ends
2. Check continuity between 2 pins on one end (shouild read open)
3. Read from each pin to ground (should read open)
4. short 2 pins on one end,paper clip etc.,ohm from other end, should read complete circuit. (short).
5. Re-assemble.
If all that checks ok it looks nasty after that. There is the ABS module that talks to the PCM which controls the Fault Lights then there is also the tone ring in the differential that activates the sensor. The 2k reading is good.

Another way to check harness would be to use a small fused 12vdc jumpered to one pin of the harness and jumper the pins on the other end then read with a test light (load). If a wire has broken and 1 strand is touching a meter will still show continuity but a test light will put a little load on it and may show up by barely lighting or not lighting at all. The more of a load the better for this check. I have never heard of a front sensor causing the speedo to not work but strange things can happen electrically. The fronts should read around 600 if you want to check.

Dave

 

[fmj]

Ok. I got my good digital volt meter and retested the old one (bad), tested the new one, 1899 ohm), tested a new one from the dealer (had to try so I bought another one an tested 1886 ohm). New one from dealer installed, still no speedo. So that should totally eliminate the sensor as an issue. Looked at the tone ring from top and there doesn't seem to be any damage. There are no wires or sensors on front wheels. Only wiring is on center of front axle for 4 x 4. Also if abs module is gone will that give me no speed? I'm back on the harness per your info. Thanks I'll keep trying.

 

[DavidC]

If the ABS module is bad no speedo as the rear wheel speed sensor goes to the ABS then the ABS sends to PCM. Both of those items get messy so let's hope you do not have to go there.

 

[DavidC]

Well crap. I do not know why I thought you had 4 wheel anti lock. Looking at this one, does your 4wd work ok ?, indicators etc.

 

[GAmes]

This is a bit out of the box, but may be of help. Bear with me. I've modified my speedo to run off the ABS sensor. My ABS module failed years ago and is unplugged. As a result my OBD port does not get a signal and I had to tap directly into the speedo input wire from the ABS sensor for my speedo and cruise control to work. The other ABS wire goes to ground. Earlier this year my speedo started to act up, sometimes falling to zero. What I found was a bit of corrosion where I had connected the ground wire to the frame. IOW, make sure the entire circuit is functional. PCM connector clean and tight, etc.