I have tried searching, but haven't found quite the same problem I'm having so at the risk of having to explain it all again to a newb... I have a 2000 F350 7.3. I started out with my batteries dying after a few days of sitting. I found the interior lights were coming on dimly, and the relay buzzing. great, got it. I pulled the fuse and ordered the dimmer/light switch. I came back next week and the batteries are dead again. Charged them, drove the truck, and then the radio starts coming on without the key on. Pulled the radio. Next day the truck starts fine, but now the seatbelt noid is going off all the time and the tranny overdrive is blinking "off" but still shifts fine, and goes into overdrive. The speedometer also works erratically... I read a post about the marker lights leaking, I looked and that's a definate possibility. my question is are all these related back to the GEM or BCM? or more problems?

 

I would hook everything back up, and when it happens pull fuse 101, 50 amp in the underhood fuse box. See if that gets rid of it. If it does, I would suspect something wrong with the ignition switch.

 

thanks, I'll give that a try.

 

All your symptoms are common with a leaky windshield where water gets into the GEM and the fusebox.

 

Do you notice it acting worse when it rains? Do you notice any wetness at the firewall area at your feet? I would pull the GEM and the fuse box and look for corrosion. That windshield leak problem that was mentioned in the previous post is very common, and I forgot about it. I would steer myself in that direction.

 

I don't drive it very often, so it's hard to say but the truck smells musty, and the carpet under the fuse box feels like it could be damp. I put the fuses back and the radio, but have not seen the symptoms reappear yet... can I spot trouble codes for this with a scanner and if so what is a good one to get. wondering if a Harbor freight is worth having. I'll pull the gem next... thanks again.

 

From what I am reading,(learning about this myself) any of the cheaper scanners won't be able to talk to the Ford GEM module. And sometimes, even if you could or if you do get some generic obdII codes, you are not going to get a code that says "GEM module bad". More than likely you will get all sorts of codes that don't make any sense, just like the symptoms you are getting don't make any sense.

I think you best bet is to pull the battery cable(s) and then pull the GEM and the fuse box and inspect them visually. If you see signs that they have been wet and there is corrosion, then you have found the culprit.

 

You were right. I pulled the gem and fuse box yesterday, and there was corrosion in the plug for the wiring harness to the fuse block. before I took it apart I drove it and everything worked fine. no corrosion in the gem. I cleaned it up and put it together, so far so good. I suspect the problem is water coming in through the marker lamps. they are aftermarket, and whoever put them on did an ok job sealing them up, but it is an old fix, silicone kind of brittle... I'll work on that now. thanks again for the help.

 

Ford had a big problem with windshield leaks. So don't dismiss that because someone cut holes in the roof. The fuse box and the GEM are very expensive to replace, so try to protect them somehow till you get it figured out.

 

thanks, will do.

 

Make sure this drain hole is not plugged





Passenger side drain hole. Grease up metal clips on step plate.

BigCamper if your carpet is damp and musty smelling please pull up your step plates and check the drain hole. Then check the metal clip for rust. Lube them up before putting the step plate back down. On the pictures one is drivers side and one is passenger. Please let us know what the fix was for your truck. Thanks.

 

thanks for the input, I'll check that as well. I did find water marks/corrosion in the wiring harness connectors to the fuse block. I will be checking now to see if I got the leak sealed by sealing the marker light holes, or looking for a windshield leak.