Honda FourTrax Rancher TRX420FA5 2019 Owner's Manual page 220

If the Transmission Is Not
Functioning Properly
AUTO (automatic shift mode):
When the automatic transmission is not shifting properly, the gear
position indicator will show "–" and blink.
See your dealer to check and restore the automatic transmission.
If the gear position indicator shows "–" and blink while riding,
perform the following:
1. Stop the ATV.
2. Turn the ignition switch to the OFF (w) position.
3. After the engine stops, turn the ignition switch to the ON (q)
position.
4. Check the gear position indicator.
If these efforts do not restore proper operation, have your ATV
inspected by your dealer.
When the "–" is blinking in the gear position indicator:
Restart the engine; drive the ATV to a location where it can be
loaded and transported to your dealer.
When the display on the gear position indicator returns to normal:
You may drive on the ATV as usual after restarting the engine.
However, we urge you to have your ATV inspected by your dealer.
210 Taking Care of the Unexpected