Try as I might, I can't find any discussion on the forum, nor in the owner's manual so I come to the great Corvette Oracle!
The HUD displays the speed both analog and digital along with a "speed sign" which is supposed (I think) to show the speed limit for the particular road on which I'm driving. I'm using CarPlay and the touch screen shows the speed limit but the HUD shows ---. Now I'm pretty sure that the speed limit works with CarPlay as my new Acura RDX has the same HUD and the speed limit shows on the screen and the HUD whether I'm navigating or the CarPlay Apple Maps is just displayed on the screen. Ideas?? Suggestions??

 

The HUD and DIC get the speed limit from the onboard navigation data. I don't use CarPlay but I do use Android Auto. Sometimes AA will have the speed limit information and the onboard nav doesn't and visa versa. And sometimes they both have the information but are different.

Android Auto has the capability to integrate with the HUD on some vehicles but GM doesn't support it. I don't know about CarPlay.

 

It gets the speed info from NAV. If you don't have NAV it will not show in HUD. Nor will the directions as you approach a fork in the road, exit etc.

In fact, I like those direction changing showing in HUD as don't have to take my eyes off looking at the windshield especially for exits as often have to be sure you're in the correct exit lane.

If you have a 2LT or 3LT it should be there. If a 1LT not!

Now if you have a 2LT or 3LT with NAV there are times mine shows - - - when it does not know the speed OR the NAV SD Card is not recognized.

 

If you have HUD then you have Nav on a C8 correct? Don't both come with 2LT and 3LT?

 

CarPlay and Android Auto are not the source of speed data to the HUD. Both the apps (e.g. Google Maps or Waze) on your phone and the car nav display GPS-derived speed data, and are usually identical or maybe off by 1 mph, briefly. However, it's two different receivers picking up those data.

 

Yep, unless you get a message like I and others have received IF using USB for music! See pic.

Someone found a partial solution I'm using. GM has only acknowledged it occurs periodically for a number of GM cars.

It's caused by NAV and USB using the same Buss and they can conflict on start up. You'll first get a message on the center screen that says SD Card removed. You have to press OK to get past that message. Then when you press NAV on the center screen (I did because I was not getting speed limit in HUD) you'll get the message shown in pic!

 

When you come to a fork in the road, take it!

 

^^^
Yep a Yogism!

 

I started this thread about heads up missing top right. I noticed the temperature made it change. Cooler the better. Now it's back to normal even on hot days.
Point is, If you have this problem, give it some time, it might be something that will go away.
Dirt, moisture, or the age-old little gremlins that always persist.
I think I posted this on the wrong thread, sorry
Larry

 

Since the above is an old post and I had not solved the problem that others have also reported, I finally have about 3 months ago!

The solution was found from a note the C8 Corvette Tech found on a GM Service program after he had downloaded that latest infotainment software that was NO HELP! It said if a SanDisk flash drive is being used this could be the issue! Now all those with the most popular SanDisk flash drives don't get your shorts in a knot!

That message on the GM site gave no reason for the statement. The Tech said they are put in by other Techs who found an issue. But as the Tech saw my Flash Drive was a SanDisk. So I decided to buy a Verbatim flush mount flash drive, and all has worked for now 4 months!

I searched the Net to see what my one-year issue could have been with the SanDisk flash drive. Several posts discussed the problem with Bootlegged SanDisk Drives! In fact they warned about buying the cheapest as I did on Amazon! Logical as my industrial experience with our leading brand Heliarc TIG Torches and parts make it obvious. Parts copiers pick the leading brand to make and sell! When our patents were up we were the one copied!

It's less likely with less known brands, like what I bought! Bought it also on Amazon but had I know the issue would have bought from a reliable source. They are no doubt also selling on Amazon BUT tough to define who is legit.

The issue is related to both NAV and the USB initializing over the same Buss and a conflict occurs. Perhaps it's a read speed issue? Don't know BUT the SanDisk flash drive I used was working on my two C7s. Perhaps the C8 system requires faster read speed. Of interest, this is not only an issue with Vettes. The same error is noted with other GM vehicles using the same infotainment system. There is a Technical Service Bulletin 19-NA-279 BUT the bottom line simply stated it's a software anomaly! No help!!

 

I'm running both a Sandisk SD card and Sandisk USB flash drive on my '23 C8 and have not experienced any problems nor system conflicts...Beware of inferior bootleg drives purchased on Ebay or Amazon!

 

^^^
Yep, we're in a rural area and use Amazon a lot. Prices for the same item can vary, significantly. Also just read that Amazon knows they have millions of bogus reviews. Some vendors were offering $15 for a positive review!

Have to be careful as "Amazon's Choice" is often not the best buy! Probably their most profit! I look out for copies BUT never thought about brand named Flash Drives or SD Cards! Am careful with batteries as FOB batteries I bought for my C7 lasted less than a year!

Opened my eyes to flash drives and SD Cards now!

 

The question was about the speed limit display, not the actual speed display. The HUD gets it from the built-in Nav map database, AA and CarPlay get it from the map database in use on your phone.

Actual speed data on the HUD comes from wheel rotation data, not GPS, just like the speedometer in the dash, as in almost every other car on the road. Otherwise, you'd lose the speed display in areas where you can't get a good GPS signal (downtown NYC, for example).