Check injector and service light on

Hi everyone I am wondering if anyone could help me my message on my display when I start my car says check injector and the service light is on I read some where it was something to do with the glow plug relay which is a pain to get to I managed to change the relay for a second hand one and re attached the battery and started my car again and it popped up again but then I used my fault reader and cleared it which I could not do before and then when starting my car again it reappeared I changed all my glow plugs first I have a fault 380 help please :) very confuzzedle