Very loud continuous beep from behind dashboard

I tried searching the forums and most comments say it's the seatbelt warning. I am familiar with that warning and this is not the same.

When I put my key in the accessory position everything is normal. When I put the key to "on" there is a VERY louse continuous beep that last approximately 8 to 10 seconds. It stops earlier if I start the truck.

There are no warning lights or errors on the dashboard. The speaker seems to be behind the driver's side dashboard behind the mirror adjustment. Does anyone have any ideas what could be causing this?

Any help would be greatly appreciated.

 

What year? This kind of sounds normal. The truck is just letting you know it's not running. I'd have to check mine to see if it does the same thing, but wouldn't be surprised if it does.

 

Have you tried putting on your seatbelt before rotating the key to the "ON" position to see if that prevents the sound?

 

Yes I have. I've had the truck for two years and this is a new sound. It is similar in volume to a smoke detector and VERY noticeable to the point that it causes pain. It does not seem to come from the same area that the seatbelt sound comes from.

It is so loud it can be heard from inside my house and it justvstarted yesterday.... after work today I'm going to pull the dash down and take a look. I tired uploading a video but it is too large of a file.

 

If you have the parking sensors I'd check to see if one is covered, loose, or damaged. Have you tried disconnecting the battery to see if it resets?

 

This ^^^.

 

Did your dealer install some sort of alarm or tracking device that is now going out? Have someone else start the truck while you lay down on the floorboard and look behind the dash and try to find out where the noise is coming from. Look for out of place wires.

 

I figured it out. The previous owner would forget to put the tailgate up and damaged it twice while backing up his trailer. He installed a piezoelectric alarm wired to the tailgate. If the tailgate is down when he tried to start the truck it would ring for 10 seconds to warn him. That would explain why I couldn't find an answer online.

 

Glad you figured it out.
I certainly had no idea, but I know there is nothing behind there on the dash that could do that.

Previous owner installed a neat trick.

Maybe you will get use out of that "safety" feature also.