It allows you to talk to the trucks computer. You can pull fault codes, enable/disable diagnostics, and I used it to change the enabled components. So when I added the brake controller, I enabled the setting in the body computer to be able to talk to the brake controller module. Then I added the menu options to my radio settings to configure the brake controller.
Just adding hardware to get the factory options after you buy the vehicle is not enough. Software changes are also required. The dealer can also make the software changes. However, a 10minutes software mod at the dealer ranges from $35 to $250. My dealer wanted $130. I thought that was too much, so I used Alphaobd instead.
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