The relay marked pwr/trn keeps clicking until the battery drains?

Hi,

That is a relay for the powertrain control module and the transmission control module. Have you tried switching it with a different relay having the same part number? Internally, the relay may have failed.

If there isn't one with the same part number, here is a link that explains how to test a relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Let me know what you find or if you have questions.

Take care,

Joe