Great write up!!! I have a 2018 GMC Terrain SLT and the reverse camera at night it just plain dangerous if you are used to using your mirrors which I do. I have complained numerous times to the dealer. The dealer just did TSB 17-NA-269 but it really did not help too much.
I proceeded to try this fix the Terrain since everything looks the same as above. I lifted pin 3 and taped it back to the harness. Unfortunately, it did not work for me. The dimmer switch will not control the back up camera display at night.
Here is what it does do before and after this pin 3 lift: At night, shift into reverse and the screen is very bright, then shift into drive and the back up camera screen stays on for 2-3 seconds. For these 2-3 seconds, the intensity of the back up camera screen drops considerably to an acceptable level!!! The dimmer even works on the screen during these 2-3 seconds. Again, this 2-3 seconds in drive with the reverse screen still on acted this way before and after the pin 3 lift on this vehicle. The problem is the dimmer still doesn't control the screen when in reverse using this mod.
Anyone have an idea for the 2018 Terrain? Thanks all!