
If you have an LG phone that is stuck in car kit mode, chances are the charger port has some type of damage or debris on the charger pins. To check for damage, shine a flashlight into the phones charger port, or look the port under a bright light, and check the gold charger pins inside the charger port.
Below are images of what to look for.

How to get the phone out of "Car Kit" mode:
To fix the "car kit" error properly, you need to send the phone to a repair center for service. However if you want to temporarily dismiss this error, as long as the phone doesn't have any bent pins, the following procedures may temporarily get the phone out of car kit mode. If your phone has liquid damage, keep in mind that the phone can over power at any time, and at that point repair would no longer be an option. For best results- if your phone has liquid damage, remove the battery and have us service the phone.
Suggestion 1- Unplug the A/C adapter from the wall, and remove the phones battery. Plug the charger in and out of the phone 10-15 times, (with the A/C adapter disconnected from the wall). This does two things- it removes any loose debris from the charger pins, and it also neutralizes any built up static electricity which can cause this.
Suggestion 2- Vibrate mode- Sometimes you can "trick" the phone by putting the phone on vibrate mode, then put it back into regular mode (usually by holding the star * button for 5 seconds). This works sometimes because when a phone is in car kit mode, the only way to exit that mode is to disconnect from the car kit. Since your phone isn't plugged into the car kit though, when you put it on vibrate mode then go back to regular mode, that may make the phone "forget" it was in "car kit" mode. It may go back into "car kit" mode later on (until the circuit board is professionally cleaned) but this is a quick fix that I found helpful in some cases.
Suggestion 4- remove the battery and use a toothbrush and a dab of isopropyl alcohol to clean the pins on the port.
To have us service your phone, mail your phone in for service.