Speedo inop, NO ABS code

Injected79 · Nov 23, 2015

Hey guys have been fighting and speedometer issue. Truck is an 05 f250.for the last 2 years about 2 to 3 times per year speedo would bounce around or drop out for a few minutes but would clear up and have no issues for 6 months then randomly it would start up again..

well now it is consistently not working. When you first start the truck to leave it will work for the first couple of miles but as it warms up it starts bouncing a little, then as it gets worse will bounce 20-80 mph, next it will then just sit at zero, what ever the speedometer on the dash reads my scan gauge reads the same which leads me to believe it is not a cluster issue. I have no abs code, cruise control will still turn on and work until speedo bounces around then it tries to stay caught up to what ever the speedo is reading. I went ahead and ABS in rear diff, no difference which I didn't expect to fix the issue. IF I look at up a vehicle speed sensor it shows one for the transmission output speed sensor. does the output speed sensor operate the speedo?

any ideas?

6.0 Tech · Nov 23, 2015

Im no sure if that one operates the speedo or just deals with trans shifting. There is a ground near the left headlight that comes loose from time to time that you should check. Seen this fix plenty of intermittent speedo issues.

Injected79 · Nov 23, 2015

it almost acts if its temp related, due to the fact of how it goes from working, to bouncing, to nothing, now im not sure if its cab temp rising, or fluid temps rising, or coincidence.

But I will check the ground also.

6.0 Tech · Nov 23, 2015

Was there any metal or anything on the rear diff sensor when you changed it?

sootie · Nov 23, 2015

same thing used to happen to my 6.4 and we could never figure it out. would turn either the abs light on or throw an abs code.

Injected79 · Nov 24, 2015

some minor shavings but nothing I wouldn't consider normal

Injected79 · Nov 27, 2015

pdumont01 · Nov 27, 2015

Sounds like a cluster issue. Have you tried smacking the dash when it acted up? You could verify that the pcm is seeing mph with a scan tool if it is you most likely need a new cluster.

Just saw you already did that. My bad.

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2015sixohno · Nov 29, 2015

What are the front wheel abs sensors reading while reading data stream on abs module? See if there is a variance between that and MPH. In my experience the abs sensors don't run the speedos anymore they run off speed sensors in the transmission. Your scan gauge is most likely looking into the speedo module for input. Get a good scanner and look into it there first. The correct tool makes all the diagnostic difference.

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Injected79 · Nov 29, 2015

i Just came inside from running my AE on it. when logged into the abs system, both front and the rear speed sensors are reading in sync and correct. logged out of abs system and into trans system, pulled up vehical speed sensor, input and output speed sensors, input and output are reading what i would expect, but vehical speed sensor when logged into the trans system is reading same as speedo for most part, speedo was jumping around a little but sitting at zero most of the time and the vehical speed sensor never went over 0.2.

My next question is wear is this vehical speed sensor? everything im finding says the vss is in the rear diff, which is incorrect atleast for the speedo side of things.

Injected79 · Nov 29, 2015

was doing some more google searching tonight and came across this, this guy had the same issues as i am having. has anybody else heard of this.

Well got truck back from the dealer last night. It took them 3 days, but it's fixed. For some reason Ford (according to the dealer) ran VSS signal thru the windshield wiper motor and then to the PCM. They said the printed circuit board on wiper motor shorted out, PCM not getting a signal. Sounds strange to me, but everything is working.

Has anyone heard of this before? Just want to say thanks for the info I got from the forum.

2015sixohno · Mar 20, 2016

I would suspect a faulty cluster (known problem in 2005 -2007) if your speed sensors at wheels are operating and input and output signals are present the data being interpreted by the cluster is not being done properly. Obviously see if you can find a schematic from where the cluster receives input but I personally have never gone farther then looking to see if all the inputs are there then replacing clusters. 99-03 have circuit board issues causing them failures. I've swapped a few of those aswell. In most cases with these trucks wearable items are usually the fault. Only other thing to check would be your grounds but being your getting signal to computers that almost rules that out being modules are working.

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