Do you mean Apple Car Play?

If you're using Apple Maps with it, you'll do yourself a favor by switching to Google Maps - it's now supported from iOS 12 on, Waze is too. Apple Maps has been a laggard relative to Google Maps and by recent reviews, it's catching up but remains less full featured and less capable.

I'm an Android Auto user in one car, it's the Android equivalent of Car Play. I will say that it works very well BUT has a few idiosyncrasies. One is as you mentioned - if you stop the car for a rest or other road stop and then restart it, the system may or may not find its way back to where it was when you turned off the car. A solution that usually works for me is to unplug (Android auto in my car needs the phone to be USB cord attached) before stopping and then plug it back in after restarting the car. Rarely, the phone may need to be rebooted, that just takes a minute.

Google maps navigation works flawlessly and route change alternatives caused by current traffic conditions (very useful when driving to or through a populated area) are solid. It even displays when there are alternatives for which the time savings don't warrant a change or when even it would appear to be a longer route.

In my car, two phones can be connected to the car IF the navigating/Android Auto phone is turned off and the non-navigating phone is connected by bluetooth first. Do it in the other order and the non-navigating phone won't connect. Also, in my car, there's no audio flow-through from the Android Auto phone. That's not a problem for me because I have my music in the car on an SD card and not on the phone. Or, it could be on the non-navigating phone or a phone or other audio device connected by a AUX cable with 3.5mm plugs to the car. That's what I do to listen to podcasts and audio books in all my cars, I use an MP3 player and an AUX cable connection.

Thanks Stax and Elmer. One problem is that I'm not completely clear how my phones connect - Bluetooth or USB. My procedure is to first start Waze one the navigating phone, do my navigating setup on the phone, then plug it into one of the USB ports in the car (does it matter which one?). (If I plug it in first, then I lose the map display on the phone). Then plug my wife's phone and start Audible (which is the audio source I have been using). It connects via Bluetooth (I don't know if I had to plug the phone into the USB, but if I don't, after 12 hour of driving, the phone's battery dies). One issue I had last week is that if I'm driving through an area where there is no cellular service (either because I don't have the account which is available (e.g. Canada), or there is really no cellular service (e.g. in the mountains)). As long as I don't turn off the phone, it remembers the route (of course, the GPS continues to work, but if I have to change my route, it gets lost). I get so frustrated I'm inclined to get a standalone Garmin GPS!

If I understand, you're describing two problems.

1) Audio source other than navigating phone. Easiest way is not use bluetooth and instead connect to the Aux input. If you need power for a long drive, get a 12V plug with USB sockets that fits into what used to be called the cigarette lighter socket. Use that for power. OR, if your car has more than one USB connection, try using a thumb drive on which you've copied the content you want to hear. Or, as before, some kind of MP3 player connected to Aux to which you've copied the content you want to hear. Sandisk units are cheap, less than $40 at Target and other sellers. Fully compatible with Audible and other sound sources.

2) Navigation functions where you don't have cell service. I can't speak to Google maps on an iPhone but with Google maps on an Android phone, there's an offline capability that in settings is called "Wifi only". What happens when you toggle that on is that it asks you to specify for download one or more "map" areas that you choose (over Wifi) that can be used offline. No cell connection needed. After the map is downloaded, the Nav function of Google maps app works perfectly normally even if the phone is Airplane Mode with the exception that real time traffic information isn't available. I've used this function many times when driving in Europe where I may have limited data capacity (if I haven't bought a local SIM card) and also when walking around European cities - take a subway, pop to the surface at the right station, and then let it navigate you as a pedestrian to your intended destination. It works great.

It most certainly would work in a car in Canada with a phone having no cell service. You'd just need to download the maps for areas you will be in, before you get there. The maps are not large in size - choosing a map region that results in a 200 MB map, for instance, would cover a very large area and would have all the normal detail available.

Thanks, Elmer. The navigation problem is that with no cell service, the app cannot find the route, hotels, gas, etc. Of course, the route it found initially remains on the phone and, using the GPS satellite, it knows where I am. The problem I had in Canada is that, after I crossed the border, everything went well, until I came to a detour. When I left the saved route, it got completely confused and couldn't find my hotel. I finally paid Verizon their daily rate for international service and then I found the hotel. Of course, if I had written down the address and had a local Montreal map, then I would have been OK, but I was ignorant/lazy!

I'm a noobie regarding audio content. I have ripped CD tracks and copied them to flash drives (which is what I use since my new car doesn't have a CD player), but if the files are downloaded onto my hone using the Audible app, I don't know how to copy them to a flash drive, especially if I am doing this en route. I need to plan in advance more. But thanks for the cigarette lighter plug suggestion - I forgot about that possibility!

Sorry, maybe my comments were too long, you may have missed something I said.

With an Android phone, you can download Google Maps (using Wifi Only toogle setting) for multple areas you select. After doing that, you chose the area you're in and then use Google Maps the same way as always, to navigate. This functions when the phone is offline with NO active cell phone connection. You wouldn't know the difference except - there's no real time traffic info or rerouting. I've done this dozens of times, it works flawlessly.

Maybe the same can be done with an iPhone. Try it.

Yes, Elmer, I got that. My iPhone works the same way; it's the lack of rerouting that's the problem.

Maybe the problem is a glitch with your iPhone using Google Maps. Find a friend with an old, no longer used Android phone with a recent enough version of the Android operating system. There's no need to have an active, current mobile contract or connection. If with a Wifi connection you can download Android Auto to it from the Google Play site (Andoid equivalent of App Store) and update Maps, it will work fine when you need to use it in local mode.

When I travel abroad, I take an old Android phone anyway rather than my newest one when I plan to put in a local SIM card.

Don't you have to have a cellular connection to get real-time routing (without WiFi)? I have no problem seeing the maps, they are already on the phone. It's getting the real-time traffic and routing that I miss.

My real question was my the last one on my OP: How do I get an app which is on the phone show up on the CarPlay screen?

I'm confused and maybe that's the problem so lets start from the beginning.

You're in the US with a phone. With my car (a VW), the phone doing the Android Auto bit and navigation shown on the car's screen must be connected to the car via a USB cord plugged into the USB socket of the car. Keep any second phone turned off/not connected to the car.

I misunderstood. If you're not getting the display on the car's screen and you've tried the USB cord connection without success, take it to the dealership and have them try it.

No, you don't need a current cell connection for real time routing. Only for real time RE-ROUTING for traffic issues. If you're navigating with Off-line maps and you take a wrong turn, it should give you turns and maneuvers to redirect you back on to the route the normal way. At least mine does.

Almost! Your second full paragraph. I do get the display on the car's screen, but the phone's screen changes to the turn-by-turn directions (when using Waze). And Waze is much more difficult to manipulate on the Car's screen than on the phone's.

Re: your third paragraph, it IS the re-routing, but not for traffic issues, but because of either a detour or I just want to change my route.

And, as I implied in my last paragraph, it's not only the GPS but other apps on the phone which I may or may not see on the car's screen, and how do I change that? I sense that I cannot.

Well, I think there are times when you are not connected, thus your problems. I have a cabin in Northern California, and there are areas where I do not get updates. I may have gps, but not cellular, and I need both.

I think your issues are cellular. Do you have a cell phone that works when your car does not.

eta: I have driven in tunnels; seems all info does not change in the tunnel.

mtv, I don't use Waze with Android Auto or otherwise. Other than the social media aspect of it, I'm not sure what the advantages are compared to Google Maps. Waze is owned by Google, I assume both use the same traffic data sources for rerouting. Since I don't use it, maybe you can tell me what other value-add instead of Google Maps.

As I explained, my familiarity with Android Auto (and CarPlay by extension) is focused solely on the Nav function as I handle audio entertainment differently. I don't think I really have other suggestions. Other than to get help from a dealer.

Jim Mat, I'm not sure I fully agree with you. I live and drive around in NorCal too. Once you get out of the built up areas, unless there's concern about traffic accidents, realtime traffic updates for route adjustments are not often needed.

If using the offline map function, a cellular connection is not used or needed.

Tunnels? I think GPS devices do a bit of what in the navigation world is called "dead reckoning". GPS units built into cars that can read speed data from the wheels whereas a navigating phone may need to do some guessing. But it's not that hard. As an example, if you're driving north-east from Oakland on Hwy 24 and the device knows you're travelling 65 mph as you ascend in the hills (both of which it knows), it knows a tunnel is approaching. There's one and only one place you'll be (based on speed traveled) x seconds after the signal cuts out and that's on the inland side of the Caldecott tunnel, still on 24.

Similarly, in forested areas, or downtowns where the sat signals are interrupted, dead reckoning may take over assuming you're continuing on your route. With offline map function enabled, my experience is that my smartphone will recover more quickly than when it's waiting to get BOTH the GPS sat signals more clearly and a better cell signal. My cars that have built in GPS seem to have fewer sat signal drops and function better.

Elmer: The benefit of Waze is the real-time traffic info. On the phone, there are two drop-down menus, one of which is a listing of all the turns, etc. being planned, and the other is a listing of all the reports from other Wazers, either automatic or manual. For example, I make a particular drive regularly and have found a route which usually works well. Last week, Waze had recommended a different route, and the ETA was 2 hours longer than usual. Using the pull-down menu, I saw that there were some severe traffic tieups about 100 miles ahead, on Waze's alternate route. I used my regular route and as soon as I did, Waze's ETA revised itself to my usual experience. My built-in car navigation system also used my regular route, but it doesn't have the link to Waze's reports.

Jim: Yes, my problems are cellular. This could be either I'm in a remote area of Northern NY (e.g. the Adirondack Mountains) where there is NO cellular service, there could be cellular service, but not my account, or be in Canada, where you have to pay an additional fee to access the available cellular service. The GPS works fine in all these three occasions.

Example: I'm driving to a trailhead to go on a hike with some friends. My GPS gets a good route to that trailhead, and I get there with no problem, even there are long stretches where there is no service. After we finish the hike, we verbally agree to meet somewhere else for another hike, and he leaves. While trying to get to that second trailhead, I get lost in the maze of unmarked dirt roads, and the routing feature is totally unusable, because there is no cellular service. I can see the roads, however, and can navigate the old fashioned way.

In this month’s Consumer Reports, there is some text regarding using the USB port to charge your phone; may cause interference with a vehicle’s infotainment system. CR recommends using the cigarette lighter with adapter.

Elmer, your experiences are your experiences, but are not consistent with mine, in an environment similar to the OP.

I am not sure why you are referencing me with real time traffic info. If I want tariffic info AM 740.

I drive the MacArthur and Robin Williams tunnels on a weekly basis and my GPS does not display correct mph. I am not sure how a 1/4 mile tunnel affects navigation is relevant to the OP.

mtvhike, Google Maps has real-time traffic info and offers routing alternatives accordingly. The updates seem like they come every minute or two, because you can see the little info bubbles on alternate routes shown on the map changing from maybe first "8 minutes longer", then maybe "10 minutes longer", etc. Same happens when on a delayed segment and the traffic flow changes.

In my two year old VW, the USB connected Android phone becomes integral with the infotainment system. Navigation by voice command entry is possible and works well, same with searches (the Google equivalent of Siri) for points of interest to choose from or navigate to or to call. I've had the same experiences using my phone in rental cars that were Hyundais, Hondas, and once a VW of a different model than I own.

To try, I just put the Google Map app on Wifi only, downloaded a map of my area, put the phone on airplane mode with Wifi off (no signal of any kind), and put in a destination I knew to be a hike off the road. It found my present location and came up immediately with directions and a route. Whether or not the last bit would have been on a marked trail, I don't know, but the phone would have given me step by step maneuvers and tracked my location. To a trail-head, no problem. I know from prior experiences you can always enter destinations by longitude and latitude, for destinations outside of built up areas. Works fine.

So yes, these are my experiences. If you're both using iPhones with CarPlay, then that's the difference. Or Waze instead of Google Maps. Or, it's something else.

I regularly take long drives so I bought what I consider to be a burner phone - a cheap Tracfone Samsung that was $60 - to use in the VW to avoid having my good phone on such extended charges and too many on and off cycles. It works flawlessly. The suggestion came from the salesman who sold me the car - he talked me out of buying the model with built in GPS that was only available on an upgraded feature line and was about $4K more. He said "buy a cheap phone and a cheap plan and spend the remaining money on something else." And so I happily did. Having a phone with a cord plugged in is a bit less tidy than having a built in unit (as I have in two other cars and in the other cars I've owned for the last 15 years) but it functions well.

" I am not sure why you are referencing me with real time traffic info. If I want tariffic info AM 740. "

haha, I missed this the first reading.

You've never used real time traffic rerouting on a capable GPS system if you think traffic reports on the radio are a substitute. It's a substitute as much as a horse and cart can be used instead of an automobile.

A GPS signal on a phone or standalone device can only measure speed when it has constant sat signals and so not in a tunnel. I'm not sure why you'd need this, take a look at your speedometer instead.

Funny, since I have email notifications turned on, I get them a lot (no problem), but last night a notification came in:

"Valy Jons said:There are many cases when you may need to find out where a person is, from simple curiosity to quite serious fears for him. Smartphone users can be mo... "

but when I loaded Houzz, nothing!