Now when i did a lil research on this for him i cam up with the VVS sensor on the rear diff. Could this be faulty to be trowing this code?

 

My dads 97 F250 7.3 did the same thing for a while. Turns out the ATF was a little low. Once ATF was added the light went out on its own. Maybe a coincidence, however. The tranny blew a year later.
On my 99 F250 7.3 I replaced the Vehicle Speed Sensor one day and the OD light began flashing as soon as I started the vehicle up after the VSS replacement. I tried to see if any OBD2 codes were showing, but nothing came back on my scanner. I ended up going to Ford for another issue and they cleared the light problem. I cant remember what the service guy said caused it on my 99, but I remember that he said it was no big deal, a quick and easy fix for him. Hope this helps.

 

Sounds like it very well could be. If memory serves me correctly, the sensor on the rear diff sends a signal to the tranny computer, which turns it into the speedometer reading using the configuration of which tires came on the truck. If the sensor fails, then the tranny computer is thrown out of whack which will throw the overdrive light. Does the speedometer flutter?

 

By the way, my speedo did not work at all after the VSS replacement. When Ford cleared the OD light, it worked again. (I know you were asking the OP) I just forgot to mention my speedo inop in my first reply.

 

when my sensor went the speedo would not work until i got up to 55mph then every thing was good are you throwing a 743 code?

 

Iam reading the code off my Edge Evolution box and it reads Transmission Slip error. Iam able to clear the code but it comes back on from time to time. and it seems to be more when iam doing around 45-65.

 

Could be either tranny, sensor or wiring. The light and code are from the PCM comparing the sensor values. The pcm outputs the slip code anytime those values are out of normal range. The hard shift is a failure strategy.

A bad sensor will cause it. Check the fluid level and overall condition. If there is a noticeable slip or long delayed shift it's likely mechanical. The driving conditions setting the code are a clue to what's causing it.



.

 

The slips are random, i have been driving with him lately, no long shifts or slipping just gets the code at random times. Like stated it happens at cruising speeds just driving not accelerating most the times. This is my view of it being a passenger.:shrug: the vss is only 10 bucks i guess thats probably place to start.

 

well I can say that I have my trans apart right now because of that pesky light coming on. Mine turned out to be that the direct clutch pack was nicely burnt.

Mine seemed to be fairly random though more frequent with the hot chip in the truck. I drove for a bit with no chip even towed 8k through the hills in TN and had no trans problems even kept trans temps in check on a 95° day. Then one day this fall I was driving to the store and just accelerating at a redlight threw the trans code. Haven't had any other real problems and couldn't trigger it by stomping it with no chip.

I had a strong inkling that it was trans internals thanks to injectors and a hot chip. But in your case without mods then the VSS would be a good place to start.

 

$10 is worth a shot. Cruising speed likely would be converter or TC clutch slip. If it's a mechanical problem w/o a detectable slip. It's a guess by the PCM as well. Nothing between engine and axle, so it assumes tranny slip. Resistance will fool it.
What you can do is check and clean contacts at connectors. Cam sensor is in the loop with the throttle sensor too.

 

Sorry for being late BigDieselPower. Before you R&R the VSS on the Diff. Ford calls it the Rear Anti-Lock brake sensor.Part # 2C190 .Ohm it out. Ford manual says it is supposed to be between 800 and 2500 ohms. if not replace it. If it is, you will have to repair Circuit 519 (LG/BK). Now this if for the 99 SD it may be a little different than yours. Mine went bad last year, and the symptoms were flashing OD on shifter, harder shifting than normal, and the Speedo only worked after 20mph. Hope this helps a little or sets you in the right direction! Good Luck

 

So i switched the sensor today and the light came on 2 times in a 3 mile time peroid on the freeway. i have the edge box and keep clearing the code with that should i go to the dealer and have them clear it? or idk where to go from here.

 

Take the + off of your batteries, and turn your headlight switch on for a couple mins. The lights wont come on, but it will drain the residual power out of the pcm, and will clear the codes.

 

Take the + off of your batteries, and turn your headlight switch on for a couple mins. The lights wont come on, but it will drain the residual power out of the pcm, and will clear the codes.

Ohm testing the circuit while clearing the codes is a good idea. You would have to do this on all related circuits to rule out wiring/harness. I have seen several chase this, replacing converter and transmission and still have the light.
Can you detect/feel a slip?

 

No I cant feel a slip it seems to be coming on when iam around 55mph. the speedo works fine and i replaced the rear ABS sensor. i also replaced the cam sensor with whats suppose to be the revised cam sensor this summer in july. and I just replaced the pan gasket and tranny filter end of dec 07.

 

OK I took both positive cables off and reset it. and she seems to be doing fine for now atleast. thank you all for your help. :smoke :thanks: :Thumbup:

 

ok back to point one here. it was off for awhile and now I got it once today. any suggestions? Internal?