I have a 98 12 valve with auto. It has an exhaust brake on it. Right now the TQ does not lock up when I use the ebrake. This thing is wired into the ebrake wiring and the loom going into the computor. So the question is what is it, and where can I get info on it so I know if it is doing it's job. I called PAC Brake and they don't know what it is. Yes the ebrake is a pac brake.

Thanks

 

looks like a relay with a ballast resistor

 

Running the number I see that it is indeed a relay. What it goes to on your truck, I couldn't tell you with what is pictured there.

http://octopart.com/65v-2-h-dc5-omron-8095571

 

It's a homemade TC lockup switch activated by the exhaust brake.
Without TC locked up an exhaust brake won't hold you back.