Asset Warranty in Oracle EAM

There is no automatic action/functionality included with Assets warranty in Enterprise Asset Management.
Field Warranty Status is a lookup code with no values seeded

Field Warranty Active can be set when creating work orders via EAM self service page (values
Yes/No). This field also has no validation in the application. Is just a reference field

Field Warranty Expiration Date can be set on the Asset number definition form or self service (OAF) page. It is also not affecting the system in any way. It is also just a reference field

In other words, even you see some fields which point to warranty, in fact none of these fields are affecting the application in any way. They are just reference fields in order for you to take necessary actions (manually),
So there is nothing to turn on based on current application functionality

What I could suggest to you as workaround is to create your own warranty details based on Asset attributes descriptive flexfields(DFF)

At least we can track warranty information for Assets somehow in this way but not for components (Spare parts) used for maintenance, this functionality is currently not available in EAM 
(Version R12.1)