I have a 2008 Chev with the integrated trailer brake controller option. The thing is flaky.
Sometimes (even with no trailer connected) it gives me a DIC message to "Service Trailer Brake System".
When connected to a trailer, sometimes it will fail to see the trailer. Or sometimes it will work fine until I stop the engine, then it will fail to see the trailer connected when I restart.
I have checked all the connections up and down the food chain, and they all seem fine. The trailer brake circuit checks out good, with proper grounds and proper resistance value.
that's what i will be doing and after the results come back decide on what fluids to change out.
In driving the truck, i have gassers now, it rides good, no funny smells , power seems good, no smoking when running over all it looks in good shape for the age. Just have to go with my gut and my time spent under the truck with flashlight looking for grease, oil leaks etc and it looked fine .front to back from below..
wish me luck and i am a member of the diesel club. :)
I think you made a good choice.