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Speedometer problem

8K views 23 replies 6 participants last post by  villestrip 
#1 ·
I've read a lot of different speedo problems but none seem to be the same as mine. Truck runs fine no problems with boost, shifting or driving issues. Truck run great. No DTC codes. Speedometer just doesn't work. Sent it in to CBM and paid for the repair but still no speedo. Any suggestions on what could be wrong? Also if I have my CTS plugged in the Speedo reads 0 mph on there as well. Is this just a VSS issue or something else? Seems everyone that had a VSS issue seemed to have a code to go with it.
 
#2 ·
Replace the sensor, it is on top of the rear diff.
 
#3 ·
Appears the VSS is also referred to as the Output Shaft Speed Sensor. Goes to three pins on PCM C3 -- Pin 22 (TPR Ground); Pin 1 VB Power; and pin 28 (OSS).

I would suspect a bad pigtail, bad wiring on the middle pin of the OSS to PCM C3-28 , or bad OSS.

5R110w variable speed sensor | eBay

If the speedometer and the Edge are not registering the speed from two different areas, I think you're on the right track. The Diagnostic bus and the instrument cluster are mysteries to me. I don't have the wiring diagram to the instrument cluster, and the how the diagnostic bus talks to the PCM and which pins is beyond me.

Long time ago, I've gotten speeding tickets before when my speedometer was not working. At least today, you could use GPS speed if you had to.
 
#4 ·
The speed sensor will affect transmission function and shift points as well.
 
#5 ·
Thats whats weird transmission shifts fine. No drivability issues or CEL. Can I use IDS or autoenginuity to see if the sensor is responsive? Or even the test mode on the factory gauges? Don't just want to throw money at it now that I'm $200 into it. :doh:
 
#7 ·
Do you know which signal goes to where? Which goes to the speedo and which goes to the ob2 port?

Also just some info I have forgotten is I do have a Truspeed installed in my truck but it's been in there for years. Also now that I think about it every now and then when I tow my speedo bounces and ABS light has come on. But it has been a couple years since that has happen.
 
#8 ·
More info on this. Got to dive the truck a little more today. I put the gauges in test mode and went to the VSS screen. It read 0 mph while I was driving as did the CTS 0 mph. So does this mean for sure its the VSS? Also if the VSS is bad I though you got a DTC. Here are some pics while driving about 40 mph. Truck still is running great and shifts fine. Also forgot to mention the odometer doesn't move either.

 
#9 ·
Went to the dealer to get a new VSS and it was $115. Didn't want to spend that much to take a chance that it wouldn't work so I ordered one from carparts.com for $15. Now I wait. Also while driving the speedo pegged out at 100 mph which read 127.4 on the VSS under the test feature on the gauges. Then it dropped to 0 mph and the started reading correctly till I shut the truck off. No CEL or ABS light.

Does anyone know what the ohm reading should be with a good VSS if I test it off the truck?
 
#10 ·
Sorry for the delay

the VSS does the speedo and if the vss is not working it is my experience the truck will be down on power ( a lot )
if your cts is not picking it up then i would imagine

the vss or tone ring is having issues

the wiring

or the ABS module since thats where the signal goes before it goes to the cluster and the pid is generated

now the fact it jumped to 100 + is interesting

i do not have OHM specs they say a oscilloscope is best but there is some Google info out there for the newer fords like this that should get you some testing method with just a meter
 
#11 · (Edited)
so you have the non OBD true speed ?

i would check the cluster and harness wire connector ( remember the Velcro strip ? ) oh and the wires to the module itself


i know the true speed is responsible for the PID signal also because it manipulates it before it is sent to the speedo

so no true speed interaction =no pid no CTS no speedo
 
#12 ·
so you have the non OBD true speed ?

i would check the cluster and harness wire connector ( remember the Velcro stripe ? ) oh and the wires to the module itself


i know the true speed is responsible for the PID signal also because it manipulates it before it is sent to the speedo

so no true speed interaction =no pid no CTS no speedo
Thanks for all the help. This stuff is confusing me. What velcro stripe are you referring to? All the cluster wires seem good. I removed the whole dash panel to pull the speedo out and to avoid bending the wires too taunt. Also the CTS and speedo both read identical whether its stuck at 0, 100, r reading correctly. Not sure if that indicates anything.
I really want to ditch the Truspeed and program my tires with AE but I don't really want to fork out that much doe right now. Need someone close by that could maybe program my speedo. Maybe after I replace the sensor I pull the Truspeed and see if that changes anything.
 
#13 ·
thats a good idea ,

my truck was not taking A/E tire changes so I had to use the true speed

that in itself was an adventure to get dialed in somthing was off in either my truck or the true speed they even sent my another to try

i had to put in something stupid like 50" tires to get my speedo to read right
 
#17 ·
#20 ·
Not yet that is next. Just weird it's been working fine now it's acting up. Guess the trustees could be bad causing the problem.

I had a similar problem where mine quit working as well does your radio not work either
Radio still works as do all the other gauges in the cluster.

Does anyone know if the ob2 port and the gauge cluster both get the speed reading from the abs module? Cause if I put it in test mode as soon as the gauge reads the cts which comes from the ob2 port get a vehicle speed also.
 
#22 ·
Update. So CBM called me on Monday super apologetic for not getting back to me sooner. We talked for about 10 minutes and I describe to him what the problem is. He says they've never had this problem before and then offers to ship me out a new speedo cluster while I send mine back so they can check over the cluster again. I thank him but ask if I can call him next week after I get home from work and try a couple ideas I have on why my speedo isn't working. Fast forward to today. My plan was to test to see if the truspeed was bad prior to tearing into the VSS wiring. I found this link to another guy having speedo problems and running a truspeed. Here's what he said on another Ford forum:



Thought I would post this since it isn't the easiest thing to find online.

Little history, I have had my speedo come on when ever it felt like working for the past year. After swapping out VSS sensors, I sort of gave up. I didn't care enough about it to thoroughly research in depth since I always knew about how fast I was going. That and I was told I needed a $900 cluster, so screw that and not to mention the value of my truck was holding since the odometer was at a standstill.

Fast forward to today...Got a hold of a Superlift CSR that knew what he was talking about.

If you have a Superlift Truspeed Speed Calibrator AND your having speedo issues this may be for you. Here are your starting options. I say starting options because if it isn't your Truspeed that is bad you may be in for bigger money fixes, like a new cluster if indeed the cluster is bad. The following is in regards to the Truspeed unit, I am not referring to the connections at your battery tho it may be a good idea anyway:

#1 Check your (+), most importanly check your (-) connections. I undid both. tightened the (+) up, and gave the (-) a good reaming with a wire brush. In my case this did not fix my issue.

#2 Disconnect (+) and (-) and tape (individually not together) them up good w/ electrical tape. Test drive. This bypasses the Truspeed module and uses factory routes to read speed tho I believe this method uses SOME of the Truspeed internals. In my case this was the fix. No more Truspeed for me. I now run 35" tires so I'm only off about 2-3 mph compared to the 38" tires I ran before. I'm leaving it like this till I completely remove the Truspeed once the weather cools down. Its 110* outside. Nuff said.

#3 Cut yellow wire and green wire. At this point you have a green and yellow going to the Truspeed and a yellow and green going toward the engine compartment. Splice the yellow and green going into the engine compartment together. This essentially reconnects your factory wires using factory routing to read your speed. Does not use any part of the Truspeed internals. If this resolves the problem you may as well disconnect the (+) and (-) connections and tape them up as well because your Truspeed is dead.


So I started out by looking at my connectors and the inline fuse and it all looked good. Then I just disconnected the positive and negative terminal of the truspeed. Test drove it. Speedo is back. It is off by a little since I don't have an AE to change my tire size but the speedo works now. Also another note I opted to buy the VSS from an online car parts place. I didn't go OEM cause I didn't want to throw a $115 OEM sensor at it and it still not work. I was able to get one for $15 and it seems to work just fine.
 
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