A few years ago, I had a strange problem, and you guys on here told me just what it was, ( cam position sensor) and I had it fixed immediatly. I don't know about this one, but I'm keeping my fingers crossed. I have 1999 7.3 L. Power Stroke Diesel, about a week ago, first I noticed strange things going on, like my ADS light came on, then the Overdrive was flashing Off. Then my speedometer went crazy, one day I was slowing down to stop when I got to about 30-35 mph it would just drop to 0. I've been working long hours, and had not had time to check into this. Then today, it seems that it has just decided die if I go over 40 mph. It will start back up, but will die again if I get to 40 mph. I've checked and noticed to that my trailer lights don't work either. Does anyone have any ideas where to start?

 

sounds like u have a bad ground some wheres,or ow voltage

 

sounds like u have a bad ground some wheres,or low voltage

 

I dont know about the trailer lights and all.But rhe a.b.s. and the flashing o.d. lights,and some driveability problems are the same that I had.I changed the speed sensor(or A.B.S. sensor at napa) for $12 and all is well.Its located on the top side of the rear pumpkin.Its held in by one bolt.I had to pry the old out with a screw driver.Good luck

 

dryfly's got it!

You need a new VSS, Vehicle Speed Sensor. It's the one thing common to all of your symptoms.

Easy to buy, locate, and change. Just use a brush or something to clear away the dirt around the sensor before you take it out so that dirt doesn't fall into the differential when you have it out.

Pop

 

Thanks for the help, I'll start there, and let you know.

 

How old are your batteries. Check the cables. Clean or replace if needed.

 

I am with Pop and Dryfly, it is the VSS 20 minute job start to finish.

 

Why is the truck dying then?

 

If I read the OP comments correctly, I think he is just saying the SPEEDO is dying, not the engine.

 

The speed sensor could cause the engine to die in addition to the other issues your having, as the PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition control, transmission/transaxle shift scheduling and torque converter clutch scheduling.

Since the VSS signal is generated by the (GEM) Generic Electronic Module and sent to the PCM, try pulling a Diagnostic Trouble Code as there is quite posibly one triggered.

Good luck,and keep us posted on your findings,


Austin

 

Ive melted my rear differential and sensor down twice, the truck kept running but the speedo didnt work. Ive also had a fuse go bad giving indications that I lost the vss. The fuse itself was losing contact on the sides but did not look burned at all. I replaced all the underdashed fuses because it was cheap and fixed what I thought was going to be a 3rd rear end. Trust me, its hard to troubleshoot on the road without the proper equipment but if its bound to happen, its happened to me in the middle of nowhere.

 

Oh, he said it is dying and he needs to restart. Dies again over 40. Not so sure this is the VSS as it seems to work up to 40. The VSS doesn't appear to be an item that quits after 40. I think we need to look elsewhere.

 

I have to say this is really the best site and you guys are awesome. I finally got a free hour to to work on this, and put a new ABS sensor in. I am happy to report that this fixed the problems with my tow lights, speedometer, all the gauges, the cruise control ( not sure if I mentioned this but it would work sometimes, not others) the Overdrive light quite flashing, I think thats its! I did not get a chance to take this out on the highway, but I'm taking it in the morning, so I'll let everyone know if the "engine dying after it get to 40mph" is fixed also. I really thing it will be, it had to be this sensor. Thanks everyone for helping. Let you tommorrow.

 

Good for you, Let us know what happens on the road.