Hi

I want to know what can be the reasons for a short in the wiring only for injector 3 and how I should approach the diagnostic of this?

Thanks.

 

The ground wire between the ECU and the fuel injector is likely touching something metal... essentially creating a CONSTANT ground. If you try another ECU to make sure that the injector drivers aren't damaged, then the grounding is the issue. You can temporarily use a test wire between the ECU pin and the fuel injector in question, clip the wire within three inches of each clip and twist in the test wire. You should be good to run then. If this fixes the issue, then you can permanently replace the wire and move on.