Glow and intake heater issues

[Duroman]

I have a 2002 duramax. For months now my check engine light is on which says I have glow plug issues. I have 275000 on the engine. I am thinking glow plugs. I know how to test them. How would I check the relay .What are the chances it is the relay

 

[2004LB7]

Please post up the codes.

If it's the federal version, you'll have a busbar or interconnects to all the glow plugs. You can test for voltage when the glow plug light is on for cold starting. You should be able to test at the stud too

 

[TheBac]

If above ^^ chances are pretty good the bus bar is rusted and broken with 275000.

 

[Bdsankey]

I agree with Jason and Tom, post up the codes and bust out a multimeter as it'll be very easy to diagnose.