Can anyone shed some light on how the internet works with SYNC 4 and various devices under the following circumstances.

#1 When you attach your phone to SYNC 4 via Android Auto or Apple CarPlay, your phone is using WiFi to make the connection. Where does the data your phone uses in that configuration come from? Is it using the data plan of the phone?

#2 If you activate the WiFi hotspot feature in SYNC 4 , you're vehicle is connected to the internet via an AT&T data plan. How do you get Android Auto and CarPlay to use the data plan of the vehicle?

#3 You can also set up a WiFi connection of the SYNC 4 system to another hotspot. For instance, I have a fully integrated PepWave router with dual SIM cards in my RV trailer. I would like to connect the SYNC 4 to the PepWave router when we take long camping trips. How would Android Auto or Apple CarPlay utilize that data connection in a SYNC 4 environment?

My point here, is that I don't want my phone chowing up its data plan if I'm paying for internet via the Ford/AT&T WiFi Hotspot LTE data plan. How do I get control of which data connection is shared by various features in the vehicle?

 

1, Your phone will use its own data if not connected to the vehicle hotspot or some other hot spot.
2. By connecting to the vehicle hotspot. While not on a 2021, my 2019 has the data plan and my iPhone auto connects to the truck hotspot once available, and in CarPlay it shows the Wifi signal in the corner instead of LTE.
3. This is a bit tougher, but I am pretty sure it won't, and your truck won't utilize it for anything of significance either. The Wifi connection for the Sync 4 system itself just enables Wifi updates, it doesn't act as a wireless repeater for other devices. In that case you would just tell your iPhone to also connect to the PepWave for data.

I will also say that I wouldn't put too much emphasis on the hotspot in the truck unless you have good reason. While it's an unlimited data plan which sounds great, it runs through a proxy that you cannot bypass and the connection speed is limited to 10 or 15 mbit/sec. It's not fantastic, I think upload is limited to 5mbit. It isn't an AT&T signal issue or anything like that, there have been entire threads where people do speed tests on their AT&T phone inside the truck using the phones LTE, then connect to the truck hotspot and maybe get 15/5.

The only reason I even still have it on our truck is we got in on a deal about a year ago where it was $15/mo for the Unlimited data plan, and our main carrier is Verizon, which has pretty much flawless coverage most places we go, but having a second major carrier as an option on long road trips has been handy. Some parts of northern MI actually do a bit better on AT&T and everyone can keep streaming even if the data rate is capped. The speed is enough for a few YouTube streams on portable devices.

 

I appreciate the response and explanation, but I believe your situation involves connecting your phone to your truck with a cable. The 2021 F150 with SYNC4 makes its Android Auto and Apple CarPlay connections via WiFi, not with a cable. The phone is connected to the SYNC4 unit via WiFi, so it can't connect to the built in WiFi sharing service of SYNC4 because a phone can't have 2 WiFi networks connected at the same time. There are 2 distinct WiFi networks being broadcast by SYNC4, one for Android Auto/Apple CarPlay and one for hotspot use. Does the SYNC4 unit bridge the data connection of the AT&T LTE internet with the Android Auto/Apple CarPlay clients?

 

Right, but you kind of answered it, the iPhone cannot connect to two Wifi connects at once. So you either have to do USB wired CarPlay and Wifi Hotspot, or just use Wireless CarPlay and the phones cell data.

 

In addition to the good points made above, I wouldn't suggest using any hotspot even with a hard wired CarPlay or Android Auto connection if that's what someone has in mind. My experience testing such setups has been that the latency from cell tower to hotspot to cell phone to Sync is such that you will receive instructions to turn at an intersection as you're driving through it. The Sync 3 and Sync 4 hotspot feature in all Ford's in my opinion is just a marketing gimmick, especially in Canada where the only carrier is Bell and data rate for it is a laughable $10 per 500MB.

 

I was really excited for the feature as our kids will watch iPads on longer trips, my wife sometimes will watch something, and while our phones have hotspot features, it's way more handy to just have it as part of the truck, especially if the person acting as a hotspot forgets and goes into the gas station or whatever with their phone.
It was a huge disappointment though to find out that they throttle the speed. That's such a lame move. I would be fine if they throttled it to maybe 35/15 or something more reasonable, but the speed they throttle it at means if more than a couple people are watching something, or if you are using it for work, you easily consume the bandwidth they allow. If I wasn't getting it for the lower price they offered for a while it absolutely would have been dropped for good after the trial. You would be better off getting a wifi hotspot from your carrier and just leaving it plugged in in the center console or something and getting full speeds and paying a roughly equivalent cost.

 

From my experience.

i can not be connected to Ford WiFi and use the same device for CarPlay.

if you connect the truck to phone’s hotspot you cannot use the same device for CarPlay

If you have a separate hotspot the truck can connect to it and use phone for CarPlay no issue.

secondary devices can connect to either phone or truck hotspot no issue with carplay

 

Just to re-cap and see if I understand it correctly.

Apple thinks everyone has unlimited data and forces your data to come through your phone carrier when using Wireless CarPlay.
Google thinks everyone has unlimited data and forces your data to come through your phone carrier when using Wireless Android Auto.

SYNC-4 has 3 active networks:

1. The internet via the AT&T LTE modem connection (shared to people in the truck via WiFi).
2. The internet via a WiFi connection you make in SYNC 4 that tells SYNC 4 to join a hot spot or other WiFi access point.
3. A private network used between SYNC 4 and CarPlay / Android Auto.

It's 2021 and these companies still don't understand shared TCP/IP networking...

 

Totally agree. When I first set up Sync4 in my truck, later that day I got a notice on the phone saying there is unusually high data usage. Because this is 2022 I (incorrectly) figured that the AT&T LTE modem would supply data to SYNC4 while my phone was connected via WiFi to CarPlay/Android Auto - but noooo - my cell data plan was feeding Sync4 instead! So now I connect via the old fashioned way - Bluetooth most of the time and USB-C when I want to use CarPlay/Android Auto. Sad.