The alarm is aftermarket and no two are the same
The way some of those alarm units are wired in is the stuff of nightmares. If you are competant with auto electrics you should be able to work it out given enough time. Otherwise an auto sparky should be able to work it out. Chances are hes seen a similar unit and will sort it in a quarter of the time it would take you or I. Loose a lot less hair in the process as well
Re manual go to gmail.com and login as isuzunz pass 4jb1turbo
download the 8 frontera attachments Then go to cnet.com and download 7zip. Use this to open the first attachment and you have a manual. If it doesnt work send me a pm with your postal address and Ill post it on cd