Ignition

Because you enable the security radio feature,I think ,the radio is connected to the keyless entry system,so because you removed the radio,you enable the security ,and that will prevent the engine from starting,I got that info upon research when I bought a ex not long ago,the CD /radio would not turn ,untill A security pin code is enter,not 100 percent sure though,made sure Google on it ,or go you tube,many instructions video there,good luck, congrats on your purchase,kept it maintained,you won't regret it,got a 1998,over 250k,before the head gasket blown,I did dove it pretty hard sometimes though,drove my niece 2012,did not like it ,so got a 1999 .