what does service code D3 mean on 2006 Honda Ridgeline

the display shows service due soon and code D3

Asked by for the 2006 Honda Ridgeline
D3 is not a service code. It is an indicator that lights-up to the right of the "D" (Drive) indicator on the dash, when you push the button on the end of the shift level. When lit, the transmission will only shift into the lowest 3 gears. It is used when hauling heavy loaded trailers or over large hills/mountains. Also helps with engine braking on steep douwgrades. See owners manual for full details. Look under automatic Transmission.
While I understand the purpose you explained of the D3.
What is the meaning when it become engaged without you pressing the button to engage it?
Thanks in advance