'99 Silverado Automatic Door Locks

[hy_69]

hi there.... last week i bought a '99 silverado ext cab 4x4... and when i bought it it locked the doors when hitting 15mph and when i turned the ignition off it unlocked both doors... yesterday it had a new sound system installed (it came with no head unit or speakers, no audio system at all) this installation included installing a new amp so the battery was disconnected for a while.. i dont know if i can blame my problem on the battery being disconnected but when i got the truck back... it still locked the doors when hitting 15mph but! now when i turn off the ignition it wont unlock the doors! and it is very annoying! i read in other forums that the procedure of holding the hi beam lever and turning the ignition on and off twice will get u into programming the automatic door locks but my truck does not respond to that... i do the hold the hi beam and turn on and off twice thing but the doors dont lock/unlock so that is not working... now.. can someone explain to me why is it that 2 days ago my doors unlocked when turning off the ignition and now they dont? any help that doesnt involve plugging a device to my trucks computer.. cause it came with the computer reprogrammed for better performance and MPG but it didnt come with the programmer chip so i cant reprogram it if another device returns it to factory settings.. thats a risk im not willing to take.... any help at all?? i know there must be some procedure involving pressing some switches or something that will re-activate the automatic unlock.... any help please!