The Diesel Stop banner
1 - 20 of 31 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 ·
Hello all,

I just bought a 1994 OBS f250 4x4 auto trans with 182k miles. The truck needs work but the body is straight and the miles are low for the price i paid for the rig. The transmission is new, installed in February and came with a new torque converter. I drove the truck 200 miles home with no issues at all other than wandering steering of course. shortly after i get home (a few days later) the o/d light started flashing randomly and it was shifting hard and is "limp mode". I forgot to mention the tach started to go out too. The tach eventually quit working altogether so i replaced the VSS and the tach sensor. After reading online i was hopeful this would fix the issue but it only fixed the tach. The tach started and still works great 2 weeks later to read but the o/d ight still comes on intermittently. The frequency is all over the place with the o/d light. it will go 5 days with no issues then it will come on three separate times in one day. sometimes it clears it self and sometimes if i pull over and shut down the truck it will clear it for a period of time. I checked fluids, all are good in the trans and are still red. Like i mentioned the trans ins very new, purchased and installed in Feb of 2021. The truck, when the O/D light is not flashing, drives great but i know that at any moment that light will start up so i really don't drive with peace of mind. I should mention this is my daily driver to and from work 8 miles in each direction so I need to get this squared away asap. I feel i have read every forum on this problem but cannot seem to find someone that has this is as randomly as me. Any thoughts on what this could be? electrical issues? TECA relay? Could this be a stored code that is still there from when i "repaired" the tach issue? I have not had the codes read but plan to do soon Tuesday or Wednesday. Is it possible this is a non issue and is something stored from when the tach stopped working because that is precisely when the o/d light started acting up. Now that the tach is fixed the O/D light is far more random. When that tach was dead the o/d light was flashing non stop.

Any advice or comments would be GREATLY appreciated. This is is my dream truck and first OBS diesel so i would love to have this thing on the road so i can enjoy it with PEACE OF MIND! Please help a brother out!

Thanks in advance,
159861
 

·
Super Moderator
Joined
·
26,599 Posts
Scan it with a Powerstroke capable scan too. There will be a code. Could be one of the shaft speed sensors on the tranny, but that's a WAG. Maybe Mark Kovalsky will be along to give you more info. HE'S the tranny guy, not me. ;)
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #3 ·
Scan it with a Powerstroke capable scan too. There will be a code. Could be one of the shaft speed sensors on the tranny, but that's a WAG. Maybe Mark Kovalsky will be along to give you more info. HE'S the tranny guy, not me. ;)
Thanks a lot haha i am hoping Mr. Kovalsky will shed some much needed light on this. I appreciate any insight regardless of who its from. Thanks and have a good one!
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #4 ·
Scan it with a Powerstroke capable scan too. There will be a code. Could be one of the shaft speed sensors on the tranny, but that's a WAG. Maybe Mark Kovalsky will be along to give you more info. HE'S the tranny guy, not me. ;)
Oh and by the way what does WAG stand for?
 

·
Premium Member
Joined
·
9,678 Posts
WAG=wild a$$ guess.

Mark will also suggest that you get the codes read, anything else and hell just be shooting in the dark.

Most auto parts stores can't read the codes on these trucks, you need one that can read heavy duty diesel trucks.

Quite a few of us are running ForScan Lite on our smart phones with a ELM 327 adapter to plug into the OBD II port.

 

·
Registered
Joined
·
13 Posts
Discussion Starter · #6 ·
WAG=wild a$$ guess.

Mark will also suggest that you get the codes read, anything else and hell just be shooting in the dark.

Most auto parts stores can't read the codes on these trucks, you need one that can read heavy duty diesel trucks.

Quite a few of us are running ForScan Lite on our smart phones with a ELM 327 adapter to plug into the OBD II port.

Thanks i figured as much for WAG just wanted to check, haha. I need to get a scan tool, may as well be now! Cheers
 

·
Registered
Joined
·
650 Posts
Hi! Murph88 You definitely, need to get it scanned as all we can do is guess at this point. For me the 2 most common causes for hard shifting over the years has either been the VSS sensor which you have replaced with no luck. The other has been a brake light issue make sure that all your brake lights are working properly especially, your third brake light won't cost you anything but a few minutes. The one time that it was caused by my brake lights it was the third brake light I pulled it apart and found that the light had gotten so, hot that it was melting the housing as well as the plug which was shorting out so, look at that closely. Good Luck! keep us posted.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #8 ·
Hi! Murph88 You definitely, need to get it scanned as all we can do is guess at this point. For me the 2 most common causes for hard shifting over the years has either been the VSS sensor which you have replaced with no luck. The other has been a brake light issue make sure that all your brake lights are working properly especially, your third brake light won't cost you anything but a few minutes. The one time that it was caused by my brake lights it was the third brake light I pulled it apart and found that the light had gotten so, hot that it was melting the housing as well as the plug which was shorting out so, look at that closely. Good Luck! keep us posted.
Wow the third brake light huh? I will look into this as i know for certain the clear light (reverse) to the left of my third brake light is out. I don't think i have ever checked my third brake light but will do so when i leave work. More pressing is getting the truck scanned for the codes. I will do this ASAP and will purchase a obd1 scanner for myself. i know this wont be the last time i need to scan it for a code. Thank you again!
 

·
Premium Member
Joined
·
9,678 Posts
Your truck may or may not be OBD 1, if it has ever seen the dealer odds are it was flashed to wake up the OBD II port.

I am not sure if if was flashed if the OBD I port will work or not.

You might call your local Ford dealer with your vin number and see if they can tell you anything about it in the records.
 

·
Registered
Joined
·
650 Posts
Hey, Murph88 when you remove the third brake light if you see signs of any melting on the housing or pigtail obviously, repair the pigtail but, also change the bulbs out to a 194 bulb which is smaller but, it doesn't create as much heat. The only downside is it is not as bright but, you will never have that problem again. Mine had melted about 12 yrs. ago so, bad that I had to replace the housing mine was so deformed from it melting I had a heck of time just trying to remove it. Ever since I went to the 194 bulbs there are no, signs of melting and I check it once a year. If you by chance have to replace your housing due to it melting like mine do not go with an LED type light as they can causing shifting issues because, of their lower voltage draw so, I have been told. You are better off going with the same one but, you might have to get it from a junk yard like I did because, at the time they were not available new don't know about now.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #11 ·
Your truck may or may not be OBD 1, if it has ever seen the dealer odds are it was flashed to wake up the OBD II port.

I am not sure if if was flashed if the OBD I port will work or not.

You might call your local Ford dealer with your vin number and see if they can tell you anything about it in the records.
Man I'm not sure if its ever seen a dealer. Its a one owner truck for 27 years. I would hope he took it once or twice but who knows. I will see what i can find out.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #12 ·
Hey, Murph88 when you remove the third brake light if you see signs of any melting on the housing or pigtail obviously, repair the pigtail but, also change the bulbs out to a 194 bulb which is smaller but, it doesn't create as much heat. The only downside is it is not as bright but, you will never have that problem again. Mine had melted about 12 yrs. ago so, bad that I had to replace the housing mine was so deformed from it melting I had a heck of time just trying to remove it. Ever since I went to the 194 bulbs there are no, signs of melting and I check it once a year. If you by chance have to replace your housing due to it melting like mine do not go with an LED type light as they can causing shifting issues because, of their lower voltage draw so, I have been told. You are better off going with the same one but, you might have to get it from a junk yard like I did because, at the time they were not available new don't know about now.
Ok sounds good, is it just those two Phillips screws on the third light housing? i took them out and it still feels hung up on something any tips or videos i can reference. Is there a tab i need to depress? I am trying to be delicate and forceful at the same time if that makes any sense...
 

·
Registered
Joined
·
650 Posts
Wow the third brake light huh? I will look into this as i know for certain the clear light (reverse) to the left of my third brake light is out. I don't think i have ever checked my third brake light but will do so when i leave work. More pressing is getting the truck scanned for the codes. I will do this ASAP and will purchase a obd1 scanner for myself. i know this wont be the last time i need to scan it for a code. Thank you again!
Yeah, I'm not sure how non-working brake lights affect the shifting of the transmission someone with a better understanding and more knowledge than I would have to explain that one. But, I do know that when you are in overdrive while pressing on the go pedal and if you tap on the brake it takes your torque converter out of lock up you will see the slight jump in your rpms so, somehow the brakes and transmission are intertwined.
 

·
Registered
Joined
·
650 Posts
Ok sounds good, is it just those two Phillips screws on the third light housing? i took them out and it still feels hung up on something any tips or videos i can reference. Is there a tab i need to depress? I am trying to be delicate and forceful at the same time if that makes any sense...
Yes, it is just those two phillips screws no tab to depress it sounds like you may have the same problem I did. Not sure about any videos but, it is straight forward it just pulls straight out but, if your housing has melted like mine did it was a pain in the A$$. I pulled the top of light away from the cab as far as I could and used a flat head screwdriver to push down on top of housing while trying to pull it out. No matter how gentle I was I still slightly cracked the lens but, once I saw how bad it was melted I replaced it anyways.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #15 ·
Yes, it is just those two phillips screws no tab to depress it sounds like you may have the same problem I did. Not sure about any videos but, it is straight forward it just pulls straight out but, if your housing has melted like mine did it was a pain in the A$$. I pulled the top of light away from the cab as far as I could and used a flat head screwdriver to push down on top of housing while trying to pull it out. No matter how gentle I was I still slightly cracked the lens but, once I saw how bad it was melted I replaced it anyways.
Good to know because i was already trying to change out that dead bulb that would normally come on when you open the doors or put in in reverse and sure enough i could not get that housing out . I will be a bit more forceful this time. and get those bulbs you are referring to. Even if it has nothing to do with my transmission issue i need all those bulbs working anyway.
 

·
Registered
Joined
·
650 Posts
Good to know because i was already trying to change out that dead bulb that would normally come on when you open the doors or put in in reverse and sure enough i could not get that housing out . I will be a bit more forceful this time. and get those bulbs you are referring to. Even if it has nothing to do with my transmission issue i need all those bulbs working anyway.
Yeah, personally I think the bulb that's in there is just too big you will see how close it sits to the housing and it does get pretty damn hot. I know most people have never had the problem of it melting the housing but, then again I know a lot of people who have had this issue. Welcome to the club. LOL Don't be upset if you break it trying to get it out you may not have a choice my friend literally had to break his in pieces to get it to come out but, once he saw how bad his had melted he didn't feel as bad for breaking it because, it needed to be replaced anyways. You are right it may not have anything to do with your shifting problems but, it needs to be taken care of due to a potential fire hazzard if it is melting the housing and plug.
 

·
Registered
Joined
·
292 Posts
If you brake it all to pieces getting it out, from what Mark told me years ago was "simply being unplugged does not cause issues" it is the being defective and plugged up that causes the issues. So unplug it and see what happens. I honestly believe that one of my trucks has been unplugged for the almost 15 years I have owned it. It has never worked both brake or dome light (had a high rise cap on it when I bought it. This is my thought for it being unplugged) and I have never had any issues. Even got pulled over one time in my old collage town (you know you will always get a ticket in a collage town). Told him the light was unplugged because I just took the top off and I forgot to plug it back up. That was like ten years ago still have never touched my light. Just my experience. Let us know what you find out .
Also the VVS sensor has been know too be very temperamental to replace. I have read several times about it being off by like a MM and causing issues.
 

·
Super Moderator
Joined
·
12,056 Posts
A 1994 diesel automatic is NOT a Powerstroke, it's an IDI. Those were all EEC-IV and OBD-I. You can read those codes with a paper clip. Here is how: Trouble Codes

Without the codes I can confidently tell you that something is wrong, and that something is NOT the third brake light. That can cause problems, but it cannot make the OD OFF light flash.
 

·
Registered
Joined
·
292 Posts
Thanks Mark, I remember now the high mount does not cause blinking O/D issues, just some other drivability issues.

Murph88: Have you climbed under the truck and checked the transmission wiring harness for anything obviously wrong, or loose? Being random the way it is maybe it could be a bad wire or ground.
As everyone says check the codes. that will point you closer to the issue for sure.
 

·
Premium Member
Joined
·
9,678 Posts
Thanks for setting us straight Mark, it went right over my head that the 94's Powerstrokes only came with 5 speeds and no automatics.

On a rare case it could be a transplant but unlikely

Sent from my SM-J737V using Tapatalk
 
1 - 20 of 31 Posts
Top