Then they can't have coded it in properly. The system will not accept a new injector code when there it a fault code.

I 100% guarantee they're not coded in correctly. There aren't many recoding devices that can do it when there's a fault code. If it's not a Diesel specialist they may not have the correct kit. They may well have a coding device, but not one that can clear this particular code AND recode it.

It's tricky even with the proper Delphi Diamand unit! I speak from personal experience of this.