The Diesel Stop banner

2000 F250 Speedometer not working, already replaced all speed sensors

25723 Views 3 Replies 2 Participants Last post by  Redwolf1017
I have a 2000 F250 7.3l 4x4. The speedometer stopped working one day. I replaced the speed sensor on the rear differential, and both front wheel abs speed sensors. Still nothing.

Here's the kicker. When I bought the truck, it had no GEM module. But the speedo worked fine. Went to the junkyard, grabbed a GEM out of a 2wd F250, installed it and drove directly to the dealer to have them reprogram the GEM. I noticed the speedo didn't work when I picked it up from the dealer. Even after they "programmed" the GEM, cruise control, 4wd switch, horn and speedo all didn't work. I took that to mean that the GEM was not programmed correctly. Contacted the dealer and they said they'd take a look again. They said the GEM was programmed correctly and it wasn't their fault. The want to charge me another 175 to rediagnose it.

Any other ideas of what could be wrong? I'm still leaning toward the GEM, but I'm fairly new to these power strokes. It just seems like the common denominator from what it sounds like it all controls.

Also, as a side note. I took it to an independent diesel shop after the dealer to get their take on it. He tells me the front driver side hub bearing needs to be replaced because of a safety issue and he won't do anything else until it's replaced. I said fine and paid 300 for that. He then refused to diagnose the speedo and other things until I okayed a $1200 repair for ball joints, u joints, another joint in the front end. Even though I had already paid his diag fee. I told him no thanks and went and picked up my truck. After I paid and was getting ready to leave, he tells me that on the side they did the hub bearing assembly, the seal was trashed and unable to be reused, so they just reassembled everything without the axle seal. On my way home the hub locker on that side fell out. I notice when I'm almost home and get out only to see that missing and the axle just bouncing around in there. Livid, I call the shop back and he tells me to ***** and to never bring my ****** truck back to his shop. The reason this is relevant is because when I picked it up the trip counter read .2 but it was at 0 when I dropped it off. So at some point they were able to get the speedo working during their test drives. That's the only thing that makes me wonder if it isn't the GEM, because they didn't mention about trying a different GEM.

Also, how hard is it to put that seal and a new locker in? I'm somewhat mechanically inclined but have never done this particular job before.

Thank you for any input, I just keep chasing my tail with this. Spent over 700$ already just trying to figure out what's wrong with the speedo lol
See less See more
1 - 1 of 4 Posts

From the service manual


The electronic speedometer receives a speed signal from the 4WABS module (if equipped with 4WABS) or the generic electronic module (GEM)/central timer module (CTM) (if equipped with RABS).

That means that if you have 4 wheel ABS, the GEM has nothing to do with the speedometer functioning. The ford dealer should have known that. But if you just had them program the GEM, and didn't ask them to diagnose the speedometer, then they might not have looked at that.

If you have 4 wheel ABS on your truck, you may need to check the ABS module rather than the GEM.

But you know what diesel shop NOT to go back to. He saw you coming about a mile away.

Here's some additional info from the service manual.

Vehicle Speed Sensor (VSS)

On vehicles equipped with 4-wheel anti-lock brake systems (4WABS), the vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4WABS module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems that require a vehicle speed signal input. Vehicles equipped with rear anti-lock brakes (RABS) generate a vehicle speed signal from the rear axle speed sensor. The generic electronic module (GEM) receives this signal (VSS_GEM) for internal use and then distributes it to the appropriate other users (i.e., the powertrain control module [PCM], speed control module, and speedometer).

Good luck
See less See more
1 - 1 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.