CarPlay will not launch on iPhone 16 Pro Max after updating to iOS 26.1 (SYNC 3 3.4.x) — older iPhone works instantly

Hello, I’m having a persistent issue with CarPlay on my 2021 Ford F-250 running SYNC 3 (version 3.4.23188). I recently upgraded from an iPhone 14 Pro (Lightning) to an iPhone 16 Pro Max (USB-C), and CarPlay worked normally on the new phone until I updated the device to iOS 26.1.

After updating to iOS 26.1, CarPlay will no longer launch on my iPhone 16 Pro Max, despite:

Using multiple high-quality USB-A →USB-C cables, including an Apple-certified Beats cable

• Performing a full SYNC 3 Master Reset
• Resetting Network Settings
• Resetting Location & Privacy
• Restarting both the truck and the phone
• Testing all USB ports
• Removing all vehicles from Settings → General → CarPlay

Here is the important part:

If I plug in my old iPhone 14 (running an older iOS version), CarPlay launches instantly using the exact same USB port.

So the truck hardware, USB port, and cable are known-good.

Additionally, on the iPhone 16 Pro Max, the truck does appear under Settings → General → About → SYNC 3, showing:

• Firmware version
• Hardware version
• Serial number

This means the iPhone is successfully communicating with the SYNC 3 head unit over Bluetooth. but the CarPlay initiation handshake never occurs when I use the wired usb a port. SYNC 3 does not support wireless CarPlay, so wired handshake is required.

Because CarPlay worked on the same device before updating to iOS 26.1, and because my iPhone 14 still works instantly, this appears to be a software-level CarPlay/iAP2 handshake compatibility issue between iOS 26.1 and SYNC 3 (3.4.x).

Is this a known iOS 26.1 compatibility issue with older CarPlay modules?

Are there any recommended steps beyond what I’ve already performed?

Thank you.