[Rickinvictoria]

Here is the problem. When the truck is cold, I use the PAC brake to help warm it up and it works fine until I put it into gear and then the PAC brake goes off and on in a pulsing manner. It doesn't matter if it is forward or reverse. This has been getting worse over time. It didn't do this last year. When the engine begins to warm up the problem goes away. I talked to PAC brake and they said it was truck related, something is causing the ecm to pulse the pacbrake solenoid, and I tend to agree with them. I suspect the ATPS but it is expensive and I am not sure that it is the problem.

Does anyone know what might be causing this or how I can narrow it down?