How do I reset the bed leveling data?

Question

I have a Creality CR-10 S5 which is using Marlin firmware 1.1.6.

I recently got a level to level my printing bed, good high precision one.

Afterwards it was printing as if my bed was not level.

I assume that the 3D printer has old bed leveling data stored from its previous calibration.

• How do I clear this old data?
• Can I enter new data manually?

The printer doesn't have auto leveling with the current firmware. I tried the old firmware, and the auto-leveling system didn't level the print bed.

I have no bed leveling sensors.