I have a 2009 GMC Chevy torrent that has a check engine light and one of the codes is a p1685 one dealership said it is my transmission module what does that do
Transmission module is the computer that sends the signals to the transmission solenoids telling them to shift gears. If the module is fried it is possible that also have some high resistance in the shift solenoids.
the tranny module possibly, is the computer if you like that essentially selects the gear and regulates the kickdown etc, you may find some of the gear functions aren't working or ereatic gear changing due to this module malfunctioning, i would certainly say this is not a job for the home mechanic and its best to be sorted professionally. I am known on here as "numb nuts" so if I am wrong I am sure someone with more experience will be happy to help out.
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