iphone 8 wireless charging in gm vehicle

Just got my iphone 8. I have a 2017 GMC Denali with the wireless charging mat on the center console/armrest. When I put my phone on this mat, the indicator light (green lightning bolt) illuminates on the vehicles display screen for about 3-4 seconds, then goes away. I can do this repeatedly. It won't stay connected to charge. I've removed the rubber matt over the wireless charger to try and get a better signal but get the same results. I've heard that maybe the mat isn't strong enough to charge the iphone 8? I've read that the GMC charging mat may only have 1 amp output and the iphone 8 may require 2 amp? Has anyone had luck getting their iphone 8 to charge wit the GM charging mats that are built into their vehicles?