Glow plug system issues

[freeride707]

Ok this isnt the normal "my truck wont start when its cold" thread I know why it wont start

Ive done the tests, My glow plugs arent being activated at the relay, now before your say its the relay and replace it, ive got 2 codes saying both GP banks are out, now how can i be getting GP codes if i dont have a GPM! if this is the issue how can i fix it?
its a Early 99 California model, so its got just one relay in the valley for the GPs it looks to also have a GPR shunt, i dont know the point of the shunt and dont understand it but it looks like its needed. HELP!!!! its getting colder and i need to fix this asap.

btw i only get the GP codes when the Chip is taken out, but the GPs dont work either way The PCM was replaced at a shop right when i got the truck the put the PCM according the VIN that should be in the truck. but it had hard start issue before that, i just let it go because it was getting to be summertime

[08pwrstrokr6.4]

your harness could be bad since its not the relay.

[freeride707]

It could be just the relay. I don't know. The fact I'm getting codes is what is confusing me I should not be able to get GP codes at all unless I had a GPM

I've tested the relay and wasn't getting power to the gp side with the key on. But if the PCM isn't telling the gps to work then I don't know how to test it