Enable Multitouch Pinch-Zoom on TBox Ultra, Plus and Ambient

Why pinch-zoom is missing

Every Carlinkit TBox can pass several fingers to Android, but the stock firmware switches multitouch on only for CarPlay mode, where it is of no use. A start-up script named sd-reverse.sh sets the property sys.suding.reverse.multi.touch when the box starts in CarPlay mode and skips it in Android Auto mode. Without that property, maps in Android Auto mode move with one finger but do not zoom with two.

All the methods below set that one property. They differ only in where they write it: build.prop on the Ultra and Plus, the start-up script itself on the Ambient and UHD 6225, or a Magisk module that overlays the script on a rooted box.

Two things outside the box also have to cooperate. The box must run in Android Auto mode, and the head unit must send more than one touch point. Owners with a Japanese-market aftermarket head unit, and with an adapter in the chain, had everything set correctly on the box and still no pinch.

Do you need to change anything?

Check before you edit system files. Carlinkit added Android Auto multitouch to the 16 Jun 2026 firmware for the Ultra 3; owners called it a surprise in the release, and the 15 Jun 2026 build for the Ultra 2 did not have it. Some Ultra 2 owners installed the Ultra 3 build and got multitouch, but cross-model installs are not supported by Carlinkit. Two owners reported that the box’s LED light stopped working on an Ultra 1 or 2 running the Ultra 3 build; one of them also had the box start only every other time and went back to the 15 Jun 2026 build for the Ultra 1 and 2.

If your box is on an older build and a newer official one exists, a local firmware update may be the cleanest fix. If you already changed build.prop by hand, undo it with adb enable-verity before that update, as described below.

Which method for which box?

If you are unsure which box you have, check which TBox do I have before choosing.

What “disable verity” means for your box

Android checks its system partition at every boot with a feature called dm-verity, and refuses changes it did not sign. adb disable-verity switches that check off so adb remount can make the system writable. On these boxes the edits then live in a separate overlay; the original files stay underneath.

That has two consequences. First, adb enable-verity restores the original system in one step, which makes the no-root methods straightforward to reverse, as long as you have not also changed files in other ways. Second, while verity is off, the firmware updater refuses to install, because it cannot verify the system it is updating. The fix for that error is the same adb enable-verity; see firmware update fails after disabling verity. Write yourself a note, or tape one to the box, that verity is off.

Root does not need verity off, which is why owners who also want Magisk modules often choose the module route instead. Neither path is safer by default: both change what the box boots, and both need the recovery package as a fallback.

Steps

adb root
adb disable-verity
adb reboot

adb root
adb remount

adb pull /system/build.prop build.prop.original
adb shell cp -p /system/build.prop /data/local/tmp/build.prop.original

adb shell

cp -p /system/build.prop /data/local/tmp

sed -i -r '/sys\.suding\.reverse\.multi\.touch/!{$s/(^.*$)/\1\n####################################\nsys.suding.reverse.multi.touch=1/}' /data/local/tmp/build.prop

tail -n2 /data/local/tmp/build.prop
####################################
sys.suding.reverse.multi.touch=1

cp -p /data/local/tmp/build.prop /system
exit

adb pull /system/bin/sd-reverse.sh
copy sd-reverse.sh sd-reverse.sh.original

setprop sys.suding.reverse.multi.touch 1

adb root
adb remount
adb push sd-reverse.sh /system/bin/sd-reverse.sh
adb shell chmod +x /system/bin/sd-reverse.sh

Verify it worked

1. Connect to the car in Android Auto mode.
2. Open a map full screen and pinch in and out. The map should zoom smoothly; rotating with two fingers should also work in apps that support it.
3. Optional: with ADB, read the property. It should print 1:

adb shell getprop sys.suding.reverse.multi.touch

If the property reads 1 but the map still does not pinch, the box is doing its part and the limit is in the head unit or an adapter between them.

Undo / rollback

Each method has its own undo inside its step. In short:

• build.prop method: adb root, adb enable-verity, adb reboot. This puts verification back and discards the change.
• Start-up script method: push the original sd-reverse.sh back, then adb enable-verity before updating.
• Magisk module: remove the module in Magisk and reboot.

Whichever you used, undo it before a firmware update. With verity disabled the updater rejects the system and the update fails; firmware update fails after disabling verity covers that error. After the update, check for multitouch first: the new build may already include it.

Troubleshooting this guide

adb remount or disable-verity fails. Run adb root first and try again. Some builds need the root step before either command works.

The pasted sed line does nothing or errors. The whole line must arrive in the shell, from sed to build.prop. Messenger apps and some terminals break it; paste it into a plain-text editor first and check it.

cp reports “not a directory” or similar. Type the paths exactly as shown, without a slash after /data/local/tmp.

The box looks dead after the reboot. It is probably still in ADB mode, so the car ignores it. Connect it to the computer, enter 142618 once in Factory settings, then try the car again. See “device not supported” after enabling ADB.

Everything is set but the map still will not pinch. Check, in order: the box is in Android Auto mode, not CarPlay; nothing sits between the box and the head unit; the head unit’s touchscreen does multi-finger gestures with its own maps; the receiver app on the head unit is up to date. Owners also noted that maps inside a launcher’s split windows can lose pinch-zoom while the same app full screen keeps it.

A firmware update now fails. Run adb enable-verity, reboot and update again, then re-apply the change if you still need it.