If you're wondering why your iPhone X is not charging on the wireless charging pad built into a GM vehicle that was released prior to 2018, here's the answer to your question.
The auto industry has already seen the demand and need for wireless charging pads to be built into their car models, and GM is no stranger to such high-tech convenience. There have been reports however, that many models in the GM family of vehicles--prior to 2018--do not accommodate the wireless charging feature for the iPhone X.
Companies like BEZALEL supply smartphone cases to bolster the wireless charging experience for techies and non-techies alike, and many reported problems with getting a proper charge in certain GM cars. The answer is that this is due to the transmitter inside the wireless charging pad in the vehicles.
Not for the GM vehicles released in 2018, but for the ones released prior to 2018, transmitters in the wireless charging pads built into the cars were just not strong enough to properly keep the iPhone X charging.
What is the solution? Unfortunately, there is no solution directly connected here for your iPhone X other than to take the step of inquiring with the company related to your particular vehicle. Popular GM cars include Chevy, Cadillac, and Buick.
While the wireless charging pads in GM vehicles prior to 2018 and the iPhone X may not work so well together, it's a bit less complicated with the iPhone 8.
Typically, as long as your hand-held device is Qi-charging capable, all should be good to go. But if you have an iPhone 8 and a GM car prior to 2018, the iPhone 8 will wirelessly charge with a little help.
To Wirelessly Charge Your iPhone 8 in a GM Car Prior 2018
If you have an iPhone 8 and a GM vehicle released before 2018, good news, the weak transmitter problem does not have to apply to you. With a certain type of phone case supplied by wireless charger specialist BEZALEL, see here on how you can wirelessly charge your iPhone 8 with a GM vehicle prior to 2018.
GM Cars Before 2018 Wirelessly Charging for iPhone 7, iPhone 6
If you're wanting to take advantage of the wireless charging pad made available in your car, one fact to keep in mind is that Apple iPhones came out with wireless charging capability starting with the iPhone 8. The iPhone 8 and iPhone X have wireless charging capability, so they will charge if placed on a wireless charger that works!
However, the iPhone 7, iPhone 6 and prior phone models do not have such capability.
Fortunately, if you have a GM vehicle that came with a built-in wireless charging pad, it will work with your iPhone 7 or iPhone 6 as long as they have a charge-receiving accessory; it will work with the charge-receiving case, such as the ones BEZALEL supplies: Latitude for iPhone 6 and iPhone 7.