Need help

Ok hear me out I'm kinda beyond over this truck rite now becuz of this problem don't take this the wrong way but I'm not an idiot I'm a diesel mechanic but grew up atound Toyota's my whole life. I have a 95 tacoma 2.7 I recently have had no spark but I hooked up a diagnostic reader to my truck just by plugging it in the plug my check engine light came back on and it starts and runs great as soon as I unplug it it doesn't start it cranks but does not run. I can't get my diagnostics scanner to work rite now or id prolly figure it out please help.