I've got some weird electrical stuff going on all of a sudden, and due to the fact that it's all occurring at the same time I have to assume it's related somehow. I'm on a trip right now so when I get home I'll research this and start checking plugs and searching more thoroughly but for now I figured I'll post this to the forum and see if anyone has any ideas. This is a 2020 F350 XLT with about 40,000 mostly-highway miles.

Here are the symptoms, all of which first occurred within about 15 minutes of each other while driving: HVAC lights are all off and controls are all unresponsive. Tire pressure sensor and tire pressure monitor fault messages. Front power windows don't work (but rear side windows and sliding power rear window work). GPS is erratic. Outside air temp display is about 25deg high. Remote unlock doesn't work and manual key unlock triggers alarm (not sure if the alarm is new - I never had to use the key before).

Since I don't yet know what modules directly relate to what, I'll mention all the other possibly-related background info I can think of: I just swapped my center console for a jumpseat and moved the entire harness over, but when I did that an airbag light came on and I haven't resolved that yet. Also my passenger door lock actuator recently failed, so the dealer had that apart and it is still awaiting parts. The lock actuator was intermittent when i took it in, but when the dealer returned the truck it has been completely non-functional. Finally, I just swapped a flatbed in, and as a result the blind spot and cross traffic system fault messages come on every time I start the truck. The installers said no harnesses were modified at all, the only thing they did was disconnect those systems I lost in the swap.

So... the airbag light, blind spot monitoring, and cross traffic alerts have known causes so I'm not as worried about those. But all that other stuff is what I'm wondering about. Nobody has touched anything for around 1500 miles and 2 days so it seems like something may have jiggled loose or developed a ground or something along those lines. Anyone have any ideas of what connectors I should check? Or might it be something else?

 

First thing I would do is have both batteries load tested, independently since they’re wired in parallel.
Next, check the large white connector on the rear frame rail, near the spare tire. Check for water intrusion or any corrosion.

When the batteries on these trucks start to go bad, it can cause some strange electrical stuff to start happening.
Good luck

 

Yeah, almost every time you get multiple electronic faults and malfunctions all at the same time on these trucks it turns out to be a bad battery or two.
Proper load testing of the batteries is the very first step, and not just voltage testing either.
Each battery needs to be tested individually, and they are tied together so at least one of them needs to be disconnected from the truck before testing.

 

Check the gray colored connector on the right rear inboard side of the frame for water and corrosion. It just before the back bumper. The ms-can makes a loop through there and when water gets in cause all sorts of chaos.

 

FWIW,

My truck was "Possessed" a year or so ago. I seriously thought I was going to have to call an exorcist. All sorts of weird warnings, chimes, no start, etc. Drove me nuts. Charged and changed both batteries. Nothing seemed to help. Come to find out when the P.O. put the truck on a diet and did some mods there was a single ground on the firewall that didn't get tightened. Fixed all of the problems. Wound up costing me about $500 with a tow to the dealer and a sharp mechanic but was money well spent.

 

Sorry I didn't follow through on here after the fact, but thank you all for the suggestions. Truck continued to drive fine and I just wanted to get home. Some of the problems started going away as I drove (some still intermittent for the rest of the drive). When I got home I did a good once-over in the daylight and just like 20fordmastertech18 said, the gray connector forward of the rear bumper was hanging disconnected and full of road salt slush and who knows what else. There were several other connectors left loose and hanging exposed too so I don't know that was the culprit for sure but that was the one that looked obviously shorted by slush. I'll spray them all out with contact cleaner and get some dielectric grease on there and seal them up properly and hopefully that will solve the problem.

As far as the batteries, I don't believe there are any issues there. They test fine with a voltmeter individually (I know, that's not the same as a load test), they are both under 2 years old, and the truck starts great in the cold even at -21F the other day. Definitely something to keep in mind as far as troubleshooting if I have any other problems.

Again, thanks for the quick replies and helpful information. It's awesome to know there's a community out there willing to help someone out.