I have a 2003 Ranger. When I tried to install a new battery, the horn started honking at about a 1-second intervals. I cannot seem to find any info on the reason for this or how to overcome it. I'm thinking it may have to do with anti-theft? Thank you to anyone who can answer this for me asap.

 

Its not the anti-theft system, PATS is passive, disables engine, no lights or horn

Only an alarm system would activate the horn and lights

Hook up the battery then cycle the key on then off and see if it stops honking
If you have Keyless entry(Fobs), then after battery is hooked up lock and unlock the doors with the fob

In the cab fuse box pull out fuse #35 that will disable the horn and horn relay, if you want