I have a 94 f350 with a e4od trans. It keep going into fault mode, when I scan it i get a code 29- Weak vss signal. I have replaced the vss and the two wires from the vss to the fire wall connection with no improvement. Once thu the firewall connection what happens to the signal and is it converted to 12 volt some where under the dash that feeds to computer. I'm begining to think the problem is in that area. Any thought or input would be appreciated.

 

Could be the PSOM (powertrain speedometer odometer module) it sets the 29 code.

 

Your Code 29 may not be a problem with the VSS but rather a problem with something starting to slip in the tranny.

The most common reason would be your torque converter lock-up clutch is starting to go. As the computer calculates that the output speed of the tranny is not what it is expecting based on the input speed from the Engine speed sensor (i.e. less than expected due to slippage) it sets a Code 29.

Note, any clutch slipping could also give you a Code 29. The problem in these cases would be with the clutch, hydraulics or control, not the VSS.

In my experience the most common reason for your Code 29 is probably your torque converter lock-up clutch starting to go.

Make sure your fluid is topped up also. When was the last time you changed your oil and filter? A plugged filter could also cause slipping.

Seb....

 

When replacing a filter after trans fluid change:

1. ensure you have the right filter 2x and 4x take different filters due to pan depth.

2. Always ensure the old filter seal comes out with the filter, check to ensure no other old seals are in the hole...... do not use a pick or you may scratch the bore.

 

The tranny is a new Jasper less than 10k on it at 4500 miles the oil and filter were changed- the level is good and it was the proper filter there was virtuially no material in the pan when the oil was changed. I did have the oil pressure gage stop working I changed the sensor anf the gage still bounces so I raplaced it with a mechanical and thought nothing of it but now wonder if the dash pannel the psom has issues with it. is there any way to chech the output voltages to the pcm to see if the psom is putting outhe proper voltages?

 

Since it is a Jasper I would call them and ask some questions............. My info relates to Star testers which Ford used to diagnose things......it deals with colored lights. Monday would be the earlist I could check for more test info at the shop online.

FYI your public profile lists a 1995 F350

 

This is real interesting to me because I just went through about a month of trying to figure out my similar symtoms.

Mine would begin after about 10 to 20 minutes of driving local but as I drove it would reset itself and work properly.

I replaced the fipl and the manual lever position sensor. Had the codes pulled but did not have any saved codes. Sometimes would run well and other times not.

Finally on a 300 mile trip it got much worse and I noticed it would begin after a bump in the road. It would still reset itself and go but returned almost imediately. I was trying to do a milage test and I reached up and hit the select button on the speedo. At the same instant the tranny went to safe mode. I hit the reset button and lo and behold it reset the tranny. Hit the select again and same thing. So I could go in and out just by hitting the button.

I called the Ford dealer where I knew I could get good advice and ran it by the shop foreman. He was amazed by the situation and said so. suggested the speedo module was bad and guessed it would be 4 to 5 hundred to get the part. But I would have to bring the truck in and have the milage recorded and order a new one. He also said that the signal fron the vss comes to the speedo first and then is sent to the computor. That would explain the symptoms. I never got any speedometer or rpm glitches so figured my vss was ok.

So I decided to take it out and look it over. Was not hard to get out maybe 45 minutes for the first time thru. Got it on the bench and looked it over but could not find any thing that looked out of place. Put it all back together and it has run perfectly ever since. I figure it must have been a bad connection at the plug and doing what I did fixed it. But the plug did not look like it was loose. I have since put close to a thousand miles on it without a problem.

Wow what a relief. The funny thing is I could have ordered the part and put it in and it would have worked. They would have said "see, that was the problem". One other thing was it would malfunction by just hitting the dash above the speedo.

So before you spend anymore time on the truck you might want to try this.

Good luck, Joe

 

Thanks Joe,

I pulled the dash to see if anything look bad this weekend and have it back in the truck. I reset it for the proper size of tire as well. It is my camper so I don't drive it but on week ends so I'll be out with it next week and see how it goes. But if this doesn't work I think I'll be buying a new psom does anyone have any recomendations on where Dash USA seem to be my best option at this point.

 

That would make what your problem was happen also.......gotta tell us the "Rest of the story"