Need some help getting my sub to work....
 

Basically its a powered sub in the trunk with a remote turn on hooked up to the back of the HU. The problem is that the sub doesn't turn on. There is power to the sub and when i discount the remote turn on lead at the sub and then reconnect, the power light comes on for one second then turns right off. The remote sub setting on the HU is set to on, but still the sub doesn't turn on.

My guess is maybe a short in the remote turn on wire that runs from the HU to the sub, but any other suggestions would be appreciated.

How are you powering the sub - new cable direct to the battery?
 

Also where have you picked up the remote turn on feed from as there are a few options on the stock HU. Also where are are grounding the sub?
If you disconnect the remote on cable, and then just connect a link cable from the perm live to the remote on connection does it work properly?
If you haven't run a proper permanent live supply then it could be the sub amp is shutting down because the power feed or earth isn't good enough.

Could also be a protect mode condition.
 

If the amp turns on for a second and then turns off it could be going into protect mode. Check for shorts between your power and groudn wires as well as shorts between your speaker leads.