I have a 97 f250 7.3 diesel. I have not had any issues till this year. In my research on here and a couple other forums I believe its narrowed down to the vss and maybe the harness to it.

Little background on this year - spring I decided to replace the batteries in the truck - had help from my son and ex hubby in hooking them up. Long story short the ex did not look closely at the idiot proof positive and negative marks on the batteries and hooked them up wrong. Smoked my alternator and also the stereo. Replaced alternator and started driving truck home truck engine revs high but transmission seems to go into neutral and then will go into gear. Doesn't happen every time I drive it just occasionally. And didn't show anything on the electrical panel or the over drive light. Had ran and drove fine for a couple of months now it is back to intermittently doing the engine rev and neutral to gear, and only now does the off light of the over drive flash, not all the time just every once in a while. First mechanic shop couldn't get any codes to read on their gun, so they flushed the transmission said no metal filings in the fluid, a little dark but nothing else found and truck runs good for age and miles.

Take truck to second mechanic to see if he can get codes. Now he can find a code on the truck that points to the shift sensor. He had the truck all last week and drove it everyday but couldn't get it to rev and go into neutral at all, wanted me to pick it up Friday. In talking with him I said I have researched on a ford truck forum and also diesel stop forum etc and everything is pointing towards the vss and the cord. I suggested he look at them. His response well I suppose I can look into it a bit more on the shift sensor code. Really? While I understand not wanting to put in parts that may not be the answer, when the code comes up shift sensor would you not check the VSS and the cord?
I had the safety recalls of the cam shaft sensor and the VSS done in 2010.

I need this truck by Oct 4th to pull a horse trailer 3 hours one way and really do not want to break down. Am I wrong in asking for the VSS and cord to be changed, especially if there is a code to do with a speed sensor?
Also could it have been fried by the incorrect installation of the batteries? It did shift goofy with in the week of the battery change then came out of it.

Thanks so much for your thoughts and help!

 

What's a shift sensor? I'm not familiar with that.

 

What was the code?

 

Where are you, there may be someone local who can help

Richard

 

I am in Southern MN said part is the local larger town has only a Midas and I do not think I want to go there. The mechanic said shifting sensor which I am thinking he meant Speed sensor but said shifting sensor. He says that makes the motor rev an the transmission go into a neutral then shift, which is what it has been doing but he seems very reluctant to swap out or check the VSS and cable under the truck.
I do not remember the code number just that its pulling a code for ss is all he says, I didn't write the number down. Sorry.

I have read on here and another forum similar if not exact symptoms and people are stating check the VSS and the cable. So I figured that was a good start and I wanted opinions from people here because I am at the point of printing out all the documentation and showing the mechanic.

 

key symptoms quoted;

what your describing has nothing to do with the VSS.the vehicle speed sensor is used for the speedomter to inform you and your trans how fast your going.there isn't anything wrong with that right?

he shouldn't have used the word "shift sensor" but maybe he didn't want to tell you what it was because he wanted to change it out for you?
at any rate,the sensor at fault that can cause the transmission to "slip into neutral." is called the manual lever positioning sensor.MLPS.
when it slips into N on it's own and you let it re-engage on it's own,it can cause a very harsh engagement.what you want to do is manually shift into N whenever that happens and coast to a stop.this way it wont bang back into gear.slowly and carefully limp the truck home and clean the sensor clip and test the sensor/replace if needed.
the MLPS is the large sensor located on the drivers side of the transmission @ the shift linkage.probably due to it's location,someone simply called it the "shift sensor" however incorrect.
anywho,investigate there,and your trans should more than likely stop shifting into N on it's own.good luck.



MLPS. this is a Manual Lever Positioning Sensor.it is also called the Range Sensor,and also the Neutral safety Switch.

 

What was the CODE?

 

if the code matches the symptoms it should have tossed code: 634

 

Thanks.
Mechanic didn't give the code number and since he cannot get it to do anything when HE is driving it, (had it since last Monday) is not replacing anything, wont even try the suggestions that anyone has given. Told me that I can drive it, since there can be so many things associated with the code.
So I will pick it up tomorrow and I guess drive it. I am supposed to make a 3 hour one way trip this Saturday and its my only mode of pulling the horse trailer. I am beyond pissed at this guy and will never go or recommend him to anyone.


I will call him in the morning and have him write down all the codes he pulled so I have them when I pick the truck up tomorrow after work. You can bet I won't even get home and it will have acted up on me guaranteed.

 

I'm not much help. Which way are you going saturday? I see you are from southern MN, I'm westof Sx Falls on I90 if you were coming this way and had any trouble.

It would be nice to know the code then maybe we can help more before you take off Saturday.

 

I am actually heading opposite of you. Going to Balsam Lake WI. I will hopefully get him to write down the code and leave it in my truck tomorrow, so that this group can help me.
While I understand the not wanting to put parts in that may not be the answer, it is I who is paying the bill for said parts, even to look into those parts would make me feel better.

 

Well then, if you look at getting a vss and/or mlps, do yourself a favor and look into/get motorcraft parts.

 

Thanks I will remember that.

 

Per request:
Ok here are the codes:


PO500 Speed sensor
PO344 Cam Sensor
PO603 communication malfunction KAM


He has not done a thing to it other than clear the codes. He has driven it everyday he claims and it has not acted up on him. So I am supposed to drive it and see if it happens again so the 3 hour 1-way trip could be interesting.


He doesn't want to replace items that may not be the issue.


Now in my mind when I have the codes above I would probably change something out.


Now with the PO603 if the batteries are hooked up backwards could it cause this malfunction code to happen?


Thanks so much.

 

Made it through the trip. Only thing I noticed a couple of times was a subtle downshift and with rpm's going up to 2. Normal driving its 1 1/2 on the rpm.

Then tonight I was driving home not pulling anything and had the cruise set, then the cruise just shut off by itself. So would it shut off all by itself have anything to do with any of the codes that were pulled? Thanks!!

No flashing od light, no check engine light either.