I wish I would have found you earlier, I spent 3 days asking people how to do this and got it to work by accident. Im not sure its correct though and have no idea what made it work.
I have an ELS vehicle in the speedo slot for a coroner. The unit works fine manually but would not respond code 3.
I ended up getting it to work by adding FLAG_LAW_ENFORCEMENT and FLAG_EMERGENCY_SERVICE and adding sirensetting value=1. Now it responds code 3, however the extra light bar on back does not work. Is that also a flag and can i get it to respond with code 3 lights and no siren?