I bought a 2003 F-250 XLT Lariat Centennial edition 2WD with 5.4 Triton w212k miles without test driving. I know…stupid…wife confirms this fact every time I’m working on it. Truck was abused, neglected and poorly serviced. One example was the original oem spark plugs. When I replaced them the electrodes were burnt down to the porcelain and the gap was almost 3/16”. Anyways I’m not going to list everything I’ve done or replaced but describe what my issues are now which leads me to believe that I might have a bad gem. My electrical problems are the following
no radio
No Wipers
no blower motor
no trip computer
no electric mirrors
No correct read gas gauge(need 7gal to show empty)

yes all windows
yes all domes
yes all locks
yes 12v outlet & cig lighter

sometimes door chimes
sometimes head lights go out
sometimes cruise control

Rarely I will get a rapid clicking sound under the dash. It seems like it’s coming from near my right knee near the bottom of the dash. Some times it sound as if there is a loose marble in that area that moves back and forth as I accelerate or brake.

i did rebuild and reseal sunroof as there was leaking when I got the truck so there may have been water leakage but haven’t had any moister evidence in the interior since. We just had 3+” and 45mph winds last night but was dry this morning.

There was no manual with the truck and the repair manual I picked up from autozone doesn’t mention the GEM at all. It’s really starting to run great now but these gremlins are killing me. It could live with everything except the head lights going out can’t happen. This just happened tonight for the first time mostly because I haven’t driven it much at night.

From what I’ve researched I don’t have some of the common probs that most with a bad gem or fuse box have. And I’m getting conflicting info regarding the location of the gem. Some say on the rear of the fuse box others say on the fire wall behind the radio. Tomorrow I was going to pull the cluster and check as some have said that there are bad connections there. The fuses all tested good but the fuse that powered the code memory acted odd when I pulled it to test.

Any ideas of where I should start?

 

On a 2003 F250 the GEM is basically in line with the transmission hump, you'll have to drop the panel on the driver side and it will be way back up under on the firewall. Barely will be able to see it and it will probably take a deep well 10mm socket to get the 2 nuts off. PIA unless you're skinny and have skinny arms too...LOL

If it were me, I'd first drop the fuse block flip it over and remove the back cover. I had a roof leak on my 2003 F350 with the 5.4L. The water traveled down to the fuse block and corroded the boards in the back, causing a lot of the same symptoms you're experiencing now.

 

Agreed. I will be pulling the fuse box this afternoon and will update with what I find.

 

Appears to be pins 10,11,12&22,23,24 on the the locking harness coming in

Not sure if thes can be cleaned up or if I need another fuse box

 

So I do also have 2 bad fuses. Since I don’t have an owners manual I’m going to try to find a schematic on the interwebs. Also some fuses locations are empty and relays but don’t know if they just aren’t used or missing. Going to try and clean it up with some electronics cleaner. I know I’m going to have to get those pins out of the harness and clean but not sure if I have the tool to get them out without f’n them up.

 

They sell the pin removal tools on Amazon. I hope you can save your boards mine were toasted. Good luck and keep us updated.

 

Looks like the consequence of a severe water ingress, probably due to a leaky windshield.

Good luck with it.