SPN 521

[Robert1966Garcia]

Good morning to one and all!
I have a 2015 International Prostar with a 2350 pushing a Eaton ultra shift automatic.
It also has the wingman collision mitigation system. I have code SPN 521 fmi 2 active on the dash.
It has the cruise no working and the trans is hard to get into neutral as you slow to a stop. Have read but can not find the existence of a brake pedal position switch, the brake lights work as they should and the trans shifts from park to drive and vis versa.
Have not found any help on line so I am turning to you folks for help. The dealer wants 250.00 for a brake light switch which I can find online for less than 40.
Thank you in advance for an help you might be able to give.

Update, I have been off for a few weeks due to COVID and low freight rates but have tried to figure the problem I am having and have learn the following.
1 the brake light switch is not the problem
2 the low air pressure sensor that the trans, brakes and traction control depends on is not it.
3 the issue, that I could find is not in the harness, connectors, tail lights Or tail light harness.
4 it only happens when the brake pedal is depressed and released, and happens if it is or is not in gear as well with the park brakes released or set.
5 you can set with your foot on the brakes till your leg gets tired and when you loose the slightest amount of air It will set the code.

I have the DLB program but don’t really know how to use it. Is there someone that I could talk too or pay them to remote in and give her a look???
I don’t want to be on the road with a check engine light on and or have a bigger problem away from home and my tools.
Thanks to each and everyone that even reads this post and the update, for your time!!