Mine was due to the main battery failing. I also had the aux replaced at the same time just as a precaution and no remote starting issues since the battery replacements done. Fyi, it’s a pita to access the aux battery. I hope this helps.
was your stop start working too or was that also not working mine isn't and I just wondered if it was a related problem they tested the main battery and said it was good. it is cold so maybe it is failing.
More than likely they just tested the main battery while it’s still hooked up and running with the AUX. That will generally yield a false positive/good reading. They need to pull the battery out and bench test it independently, verify the cold cranking amps. Mine was a 2020 with 20k miles for reference, so if you are in that range the batteries are probably close to expiring. Strange things start occurring when batteries begin to fail.
