2018 Mazda 3 - Smart Start Module error

[ranchero]

Story: 2018 Mazda 3. Someone disconnected the battery and installed aftermarket horn. They swear they didn't touch or break anything. Horn connected directly to the battery, so it's out of question.
After connecting battery both smart keys stopped working. Emergency start still works (when smart key is near start button), but there's key sign on the dash.

Then owner called me. I came thinking key reprogramming would be enough. Both keys checked, working. I successfully reprogrammed both original keys (did all keys lost), but nothing changed. Still only emergency start, remote doesn't work. I've read errors - B13D3:97-8A PATS transmitter and U201F:11-8A - External receiver. Tried to wipe them - no luck, errors remain. Checked live data - nothing unusual, except Module Supply Voltage +B3 is zero. I checked fuses - under the hood and by the left driver's foot - all fuses are good.

Does anyone know what the problem could be and what is Module Supply Voltage +B3?

[key4man]

The horn is an integral part of the immobilizer system as soon you do programming ' models from 2017 and up. When u go to programming there is a wait of 7 minutes and then u Hears beep , According to the problem u mentioned I think something in the identification system went wrong.

[Manta1600]

I asume that they disconected the battery with ignition ON and when they connected back they burn this module or blowed some fuse that you can't see or some relay is faulty

[ranchero]

The horn is an integral part of the immobilizer system as soon you do programming ' models from 2017 and up. When u go to programming there is a wait of 7 minutes and then u Hears beep , According to the problem u mentioned I think something in the identification system went wrong.

No, original horn still works, and it did honk during programming. Additional horn is totally separate with separate button under the dash.

I asume that they disconected the battery with ignition ON and when they connected back they burn this module or blowed some fuse that you can't see or some relay is faulty

I guess it's possible. I did my best to find issue, but without wiring diagram and with limited time couldn't find it.
I found this page suggesting to disconnect battery and check all connections. I checked as much wires under the dash as I could see, for more - lower dash disassembly would be required so I gave up.

https://www.hexorcism.com/16ND/sm355910/

[ranchero]

Follow up on this. I left that car alone, so I guess customer took it to the dealer. I asked him today how they fixed it. His answer - "they did hard reset, everything went back to normal".
Does anyone know what is this "hard reset" on Mazda and is Autel MS908 able to do it?

[Manta1600]

Follow up on this. I left that car alone, so I guess customer took it to the dealer. I asked him today how they fixed it. His answer - "they did hard reset, everything went back to normal".
Does anyone know what is this "hard reset" on Mazda and is Autel MS908 able to do it?

I asume something like parameter reset on the Fords

[amar28]

This is similar to JLR cars especially jaguar XF, try remove battery when ignition is on and key within proximity

Most times keyless stops working, need to reset RFA module, car loses the key sync, emergency start works but no remote

[ranchero]

This is similar to JLR cars especially jaguar XF, try remove battery when ignition is on and key within proximity

Most times keyless stops working, need to reset RFA module

How this is done? I've disconnected car battery more than once, it didn't help.