98 GMC sierra horn won’t stop honking

[nauju]

I swapped the dash on my 1998 gmc sierra and the dash I got came out of a 1998 suburban and when I got everything hooked and I plugged the battery in and the horn is honking all the time and won’t stop I had to take the relay out so I would stop, what could be my issue?

 

[thinger2]

I swapped the dash on my 1998 gmc sierra and the dash I got came out of a 1998 suburban and when I got everything hooked and I plugged the battery in and the horn is honking all the time and won’t stop I had to take the relay out so I would stop, what could be my issue?

Can you start it while the horn is going off?
If it starts and runs then it is probably not an anti theft/ alarm problem.
Try it again with the hood and the doors closed.
Does it start?

Make sure the dope light is set to come on when you open one door at a time.
If it fails any of the door open tests you may have a bad door switch.
Try that first but I suspect you may have an anti theft relearn problem.
Try the swictches first.