I should point out my bike is not a Carrera (=Cerrera?).
The bike I would like to add a throttle to is a NCM Moscow, however I also have a conversion I did to an old push-bike with a Voilamart kit. Although this has a conventional throttle input I've been using it as a testbed for adding throttle functionality via pulsing mimicking the PAS signal. As indicated, I've not been able to achieve this using the cdrskull approach.
I've also had no joy using a simpler approach published as:
https://www.mathieupassenaud.fr/electricBike/
I've done quite a bit of playing different tunes on this proposal.. it's much simpler code which I understand!
Before I try to teach granny to suck eggs, how experienced are you with Arduino code, as I generally find it "unstable" ...if you upgrade the Arduino version, functioning code sometimes ceases to function and it's sometimes picky about the peripheral detail. fwiw I'm using v 1.8.12 with a Chinese nano Arduino.
Does the code compile ok for you and does it upload without an error?
Would you like to give the Pedelecs reference to the cdrskull discussion to keep Fat Rat happy?
...discussion to be continued