[rrdregs]

Turn the ignition switch to ON.

Press and hold the 1 and 6 radio preset buttons, and turn ON the radio.

The display toggles between two screens: U with the first 4 digits of the serial number (U2200 for example,)
And L with the last 4 digits of the serial number (L0055 for example.)

I tried to do this, but in this version does not work, when the key is pressed it is already on the tele message of the number of the code, it stays on it does not turn off.