i can't get any 4k content to play on my tcl 4k tv, everything looks like regular hd and the info says 1080p.

Diagnosis

The primary cause of this issue on the TCL 43S446 is that the TV's HDMI ports are defaulting to a legacy "Auto" or "1.4" mode, which caps the signal bandwidth at 1080p. Even if you have a 4K source device, the TV will negotiate a lower resolution handshake to ensure compatibility, resulting in the "1080p" readout in the information banner. This is a common handshake failure where the TV doesn't automatically trigger the High Speed HDMI 2.0 protocol required for Ultra HD. Furthermore, this can be caused by "EDID" (Extended Display Identification Data) mismatches. If the source device—such as a PS5, Xbox Series X, or an external 4K streaming box—doesn't receive a clear signal that the 43S446 supports 4K at 60Hz, it will downscale the output to 1080p to avoid a black screen. You can confirm this by checking the "Display" or "Video Output" settings on your source device; if it lists "1080p" as the maximum available option despite the TV being 4K, the port configuration on the TCL is the bottleneck.

How to Fix It

To force the TCL 43S446 to accept a 4K signal, you must manually override the HDMI mode settings for the specific port you are using.

1. Using the TCL remote, press the Settings button (gear icon) or navigate to the Home screen and select the Settings gear in the top right corner.
2. Scroll down to Channels & Inputs and select Inputs.
3. Select the specific HDMI port where your 4K device is connected (e.g., HDMI 1).
4. Locate the HDMI Mode setting. It will likely be set to "Auto." Change this manually to HDMI 2.0. This unlocks the full 18Gbps bandwidth required for 4K content.
5. Exit the menu and return to your source device.
6. On your source device (e.g., Apple TV 4K or Nvidia Shield), go to Settings > Display & Resolution.
7. Manually select 3840 x 2160 (4K). The TV should now display the "4K" or "UHD" badge in the top right corner of the screen for a few seconds.

If That Didn't Work

• Swap to a High-Speed HDMI Cable: If you are using an old cable from a 1080p device, it may lack the wiring for 4K. Ensure you are using a cable labeled "Premium High Speed" or "HDMI 2.0." A cable that is too thin or lacks the 18Gbps rating will cause the TV to revert to 1080p to prevent signal flickering or "snow" on the screen.
• Check the Source Device's HDR Settings: Sometimes the TV will refuse 4K if the HDR format is mismatched. Go to the source device settings and toggle HDR or Dolby Vision off and then back on. This often forces a new handshake that triggers the 4K resolution.
• Perform a Power Cycle (Cold Boot): Unplug the TCL 43S446 from the wall outlet entirely. While unplugged, hold the physical power button on the bottom of the TV frame for 15 seconds to discharge the capacitors. Plug it back in and restart the source device. This clears the HDMI cache and forces a fresh EDID handshake.
• Test a Different Port: While all ports on the S446 are generally 4K capable, some units have a "preferred" port for ARC/eARC (usually HDMI 1). Try switching your 4K device to a different port to rule out a physical pin failure in the HDMI socket.

Heads Up

• Avoid HDMI Extenders: Using HDMI switchers or long extensions (over 15 feet) often degrades the signal, causing the TV to drop from 4K to 1080p automatically. Connect the device directly to the TV.
• Update Firmware: Check Settings > System > Software Update. TCL frequently releases firmware patches that improve HDMI handshake stability and 4K detection.
• Avoid "Game Mode" for Setup: When first configuring 4K, turn off "Game Mode" in the Picture settings. Some versions of the S446 software can conflict with 4K resolution negotiation when Game Mode is active during the initial handshake.