My o/d light keeps coming on, I've changed my fipls, vss, and cleaned and dielectric greased the connections on my instrument cluster.Adjusted the fipls to 1.2~3.9. The only thing I have not done is clean and dielectric grease the connections on the trans side. every thread I check about a bad psom says something will act up all of my gauges work and have never acted funny as long as I've had the truck. I have a 1994 Ford F Superduty 7.3idi with an E4OD Dana 80 dual rear drive. Before I start doing stuff on the trans I was hoping to talk to some one who has experence. As far as i know right now the only connections I have are two;1 a shift solenoid connector,2 the main connection for the trans. I'm just a green house mechanic, I only know enough to get me into trouble.

 

So I've been reading and have narrowed it down to bad connections on the trans. I'm going to buy new connectors but I don't know which ones they are yet. I'm going to keep researching but if anybody knows it would really help.

 

I haven't got one so can only pass on what I've read in these forums. But cleaning the connectors thoroughly and protecting them from corrosion seems to be a popular fix. Other e40d owners will probably come in on that

 

Does the light come on, or does it flash? If it comes on by itself the problem is in the wiring right at the end of the shift handle inside the column. If the light is flashing you're wasting your time and money trying to fix this without knowing what codes are stored.

Here's how you can read the codes: Ford ? OBD Trouble Codes

 

The trans acts normal until it's time for it to shift then the light starts blinking and into limp mode I go. Then I shuty truck off, restart(because this stops the flashing o/d light) and drive home to bang my head aginst a wall.

 

What codes are stored in the computer's memory?

 

The only code it throws is 29,insufficient input from vss or insufficient input from psom. the first time i ran it it threw 23 and 29 but i just forgot to hold down the throttle.

 

So cleaning the connectors on the trans isn't a bad thing, but it isn't going to make any difference. Your problem is either the speed sensor on the rear diff, or the wiring to the sensor, or a bad PSOM on the back side of the instrument cluster.

 

I have bought two new speed sensor both can't be bad. I soldered new connectors on the vss and the fipls. Would the psom act up in any way if it was bad? Mine has always been normal never acted weird in any way. I pulled the instrument cluster and cleaned and dielectric greased the psom connector. I'm not saying you are wrong I'm just hoping that there might be something I'm not explaining right. This is my first time doing this kind of stuff. Is there a way to test the speed sensor. Im sure I got the wires right when i soldered them, there are only two. Green and pink. I read that I would have to have the rear end jacked up to test the vss while in the truck. Not my first choice because I have a dana 80 dulley and an old green house to work in, but doable if you think I need to. Also when I first got the truck I resealed the rear diff with ultra copper silicone and a gasket. It drove perfect for a week and then started acting up. I didn't know how to pull codes at first so I got 23 and 29, changed both the fipls and vss. Nothing. Then I changed the connectors for both, still nothing. Had the truck towed home because I didn't want to drive 30 miles in limp mode. When I start the truck and drive it the o/d light doesn't start to flash until it revs past where I think it used to shift. I think that I'm starting in 1st or second cause I don't have to rev it up at all to get it moving. In the morning I'm going to check out the speed sensor, I'll run a continuity check on the sensors and see if they're the same. See maybe if I can do a continuity check on the wires, If I end up needing a psom do you know of anywhere I can get one. Is there a relay for the vss or psom? Thanks for everything

 

There are no relays for any sensor anywhere in the truck. I don't know why you would jack up the rear wheels to test the VSS. That doesn't make any sense.

If the PSOM was bad it would act up. It would set a code 29, make the OD light flash, and it would make the trans go into limp mode.

 

Mark Kovalsky, first off I want to say thank you very much. Secondly anyone who doesn't listen to you is a fool. I took the speedometer out of a 1994 bronco that I have to restore, it has less miles but now no o/d light flashing and shifts lIke normal. I've seen something on another thread about reprogramming the psom but can only be done a number of times.

 

One way to test a VSS is to get the vehicle up to about 30MPH and look for ~5V AC on the VSS leads. Obviously, doing this is kind of hard with the vehicle going down the road, but jacking the wheels up and running it 'in place' works.

I did this myself to see if I could use my '88 VSS with a cruise module off a '97, and I ended up with ~3V AC at 30MPH.... which turned out to be enough.