OK, I finally got a few minutes to get back to the truck. I followed the instructions to bypass the controller (by removing the white wire #4 and grounding that connection). I did not get any power to any other terminal on the relay (other than the battery cable #3 that is always hot).

If I provided power directly to 5A, I do get power to the glow plug wire at the plug (at least the one I tested). Given that, my guess is that (at least) the relay is bad? OReilly's wanted $70 for the relay. That seems high?

I wanted to make sure I understand the layout of the controller/relay, so I removed it and put the picture below:



Here's my best guess. Am I correct?

1. Signal to WTSL
2. Ground for the controller
3. Power from battery
4. Ground signal from controller telling relay to close (white wire from controller)
5. (a & b). Power to the glow plugs? (yellow wire from controller to 5a, green wire from controller to 5b, two brownish wires from harness attach to 5b)
6. Ignition Switch (red wire from controller, two red wires from harness attach as well). There isn't any power to this terminal at any time in my testing.

Is there a good way to diagnose the controller and/or relay while it's off the truck?

Thanks,

Jason