Thanks for the reply. It worked fine just 1 day this past week, then back to the 50% speed. Weird. Hoping maybe a future update fixes.

Obviously, there is no Waze support in CarPlay, so do you guys have the issue as to whenever you try to use the Music App in Carplay, (or any other app?), Waze goes away and the music app is launched on the phone, having you go back to the phone to launch the Waze app again?

I notice when I have my phone connected with USB, the actual speed shown is half. Speed works right until I connect with USB.

IPhone 6Plus
2106 GMC Sierra

Is there a setting or something I'm missing.

I agree. I have a 2016 Colorado with the issue. Not sure who's at fault and no one seems to care.

I have this issue as well in My 2016 GMC sierra. Same situation on my phone and my Wifes phone. Interestingly enough the Car was in the shop and I was given a 2019 Sierra as a rental and guess what, It showed the correct speed. I think there is someting up with the 2016 intellilink systems

I have a 2016 GMC Canyon with Carplay. I use the Waze app on my phone while it is plugged in to the vehicle USB port and therefore Carplay. The speedometer in the Waze app always reads about half of what I am actually traveling. There was a thread on here about it from September 2016 but it did not get anywhere. I opened a ticket with Waze after doing my troubleshooting and their response was that they do not support Carplay. I am using the application on the phone though and not projecting it to the vehicle screen.

I found that if I leave the phone connected to Bluetooth and do not plug in the charging cable the speedometer reads normally in Waze. As soon as I plug it in and Carplay is initialized on the phone it goes to half. Does anyone know a work around or something else to try or are we back to Waze just not supporting this with Carplay? To me enough vehicles come equipped with Carplay now that Waze should be looking in to it. Here is what I have tried so far. I don't mind sending logs when the problem occurs if someone from Waze will look in to it. Thank you all for the feedback.

1) Tested with several versions of Waze and iOS. Currently my phone is updated with 10.3.2 which came out today I believe.
2) Forgot the Carplay connection on the phone and set Carplay back up in the vehicle.
3) Uninstalled Waze and reinstalled.
4) Verified that I did not have Kilometers selected as the speed measurement however even then the calculation would not add up.
5) Checked my vehicle Navigation unit to make sure there were no settings for Carplay and/or Navigation that could cause this. I did not see any that looked like a culprit.

I too have experienced this and find it quite annoying. I have in fact turned off "CarPlay" on my radio in my GMC and then and only then does the speedometer in the Waze app show correctly. As soon as I turn the CarPlay back on in the radio, the speed is cut by 50% like you mention.

This used to work without issue when connected to a carplay enabled stereo and was broken within the last couple of updates to Waze.

Old thread, but annoying bug persists even on newest iOS and dozens of Waze updates through the years.  I don't care if there is an issue with 2016 Intellilink or not, this should have been fixed by Waze by now.