A master tech friend of mine suggested that when you do get circuit code for a injector to first run the injector self test. After you have ran the self test swap the connector for the bad suspect injector for a good one so lets say the number five injector harness move to the number 3 injector and the number 3 injector to the number five. Run the injector self test again. If your original code was for the number five and now after the switch and re-test it is the number 3 then you can rule out the FICM and wiring and it will most likely be the injector that has failed.
