Since the official Ford document lists a common upgrade kit for the MKX and C-Max Energi, I'm posting this here in case it helps someone else:
https://static.nhtsa.gov/odi/tsbs/2021/MC-10204043-0001.pdf
I can report a successful self-upgrade to 4G.
I found a 4G TCU from a 2018 MKX on eBay for just under $100. Things to look for:
- The FCC ID of "LHJ-FANW" indicates a 4G modem. There are a few other IDs for different model vehicles that are 4G as well.
- The maroon antenna plug is the 4G plug. If there's a second plug there that's tan, that's for the wifi hotspot. All 4G modems will have a maroon plug, a TCU that supports Wifi will have the second plug.
I made some room in the trunk.
The passenger side cover pops loose, but it take a fairly significant amount of force. I didn't remove it entirely, just enough to pull the top back and get at the modem.
Before disconnecting the modem, I pulled up Forscan and trended all values available in the TCU:
Then I unplugged the factory TCU and plugged in the new TCU. Once booted, the TCU showed several DTC error codes - lost communication with ECU, no antenna, and a couple others. I saved the As Built of the TCU in an as-found configuration.
At this point, and I'm not 100% sure it was necessary, but I disconnected the vehicle battery for a couple of minutes to give everything a good reset.
Once reconnected, I went into the LincolnWay app and deleted the vehicle. I then went in and re-added it. It was able to find the vehicle and sent an activation request. In a few seconds the request popped up on the Sync 3 screen and I authorized.
The app still didn't show I was authorized even though I got a confirmation email stating everything was good to go, so I logged out and logged back in to the app. Once I did that, everything worked and I was able to lock, unlock, and start via the app.
Here's what the TCU looked like after the upgrade:
I don't have an antenna hooked up, but I was able to easily activate from inside of my closed garage. I think the connector the TCU wants is a TS9 female, so I'm trying to find something that will work.
Other than that, it looks like I'm good to go for another decade or so until they decided to sunset 4G, too. ?