I recently bought a used 453 from a dealer and it originally came from the same Car2Go rental company, after several frustrating weeks of trying to return the car back to factory specs I was successful and to save you the same frustration here it is. Read it all before you do anything. (I've been a auto mechanic for about 40 years now)
The top left vent and box is removed by one screw reached from behind the front dash cover, buy a replacement vent cover online from a Mercedes parts house for like $30 and it pops right into the same spot and returns the car back to normal. You only have to pop out the left side of the dash below the vent to reach the Philipps screw holding in the vent and its attached box.
The one at the base of the windshield (held the rental GPS) is held in by probably two phillips that face the driver, very easy to remove. Also, you buy a replacement cover for the hole once you remove it for about $30 from Mercedes and return the dash back to normal like nothing was ever there.
Removing both items should take you less that 5 mins. You can stuff any wires back into the dash, they went to GPS equipment removed and do absolutely nothing for you or the car now.
Replacing both covers and the car looks exactly as it should as if you bought it new.
For the radio, the rental company does leave in a very decent GPS system and a full set of detailed US maps, but the car's internal GPS antenna is disconnected. Everything you need to get it working properly is still installed in the car.. (If you are unable to set the clock on the radio it is because it only can receive a time change from GPS satellites, this confirms your car's GPS antenna is not connected)
This is how you return everything back to factory GPS functioning radio and enjoy a very useful voice controlled GPS and maps again.
1. If your clock time is wrong and the menu button on the radio for changing the clock time doesn't work it means you have no GPS antenna plugged into the back of your radio.
2. You will need to watch the video before you try to remove the radio so you don't break anything, watch it here:
3. You will need to download a SmartUSA radio software update and have it ready for use on to a USB stick to update the radio, the USB stick should be blank except for the update, all 453 GPS radios required this update at some point after 2019. You can get the official software and update how-to instructions from SmartUSA here: https://www.smartusa.com/resources/downloads/maintenance/SMART-MEDIA-SYSTEM-SOFTWARE-UPDATE.pdf
4. Once you take out the radio you will probably notice there is a spot for a round plug on the back of the radio that has no plug there. If so, you will probably also need to take out the plastic mounting extender that the radio itself was screwed into, this will give you more room behind the dash. You do not have to remove the dash, only the radio and it's mounting box that are on top of the dash.
5. What you are now looking get your hands on is a Green or Blue plug stuffed off to the side somewhere back inside the dash among the other wires, this plug is not plugged into anything, it's just a free hanging wire that should be close to where the other radio wires are located. Your radio GPS plug was unplugged by the rental company to plug their GPS wire into your radio. Find the plug and snake it how you need it to get it to plug back into your radio. Once you plug the GPS cable back into your radio you are done. Put everything back together, your clock should now be working if you have a clear view of the sky for the satellites and are not parked in a garage or similar structure.
6. Now follow the radio upgrade instructions from the SmartUSA download site.
7. Several things you first need to know about the radio upgrade software.
a. It is impossible to mess your radio up, it is only an update to your radio, not the full-blown operating system.
b. All US 453 car radios use only a USB for updating, all non-US or UK and EU 453's update only from a flash card. There is no flash card installed in any US sold 453, only a USB port.
c. Find on the radio within the menus the option to reset your radio back to factory, you may probably need it.
d. Installing the update should not take more than 15 mins, but always let it finish successfully or let it error out with a message so you can try it again.
e. I had to reset my radio back to factory 6 times before I got the update sequence correct, resetting the radio back to factory after getting the failed-update message only removes your update attempt, the radio always works as it did before.
f. If you do everything correctly your clock works and now the GPS panel on the radio should show your current location. The GPS voice guidance and steering wheel voice button will also work.
g. If all else fails just repeat steps C and D until you figure it out.
h. Repeating steps C and D will return any 453 radio back to original settings, the upgrade software reactivates the preinstalled maps.
i. Resetting the 453 radio will display a message there is no maps installed, actually they are installed but the radio can't access them until you install the upgrade software, this error message is normal after all resets.
j. None of these steps interfere with the bluetooth to phone abilities.
k. You will naturally have to reset your radio station presets after any radio reset.
If you do it all correctly you will have a really nice radio and the US maps are great, we use them all the time now with the find-an-address by voice commands while driving.