Android Auto Connection Error 21

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Android Auto Connection Error 21: A Troubleshooting Guide

Android Auto is a fantastic system for keeping you connected and entertained on the road. However, encountering errors can be incredibly frustrating, especially when you're just trying to get navigation or music going. One such common culprit is "Connection Error 21."

What is Connection Error 21?

Error 21 typically signifies a problem with the fundamental communication link between your Android smartphone and your car's head unit. It's often a general "unable to establish or maintain connection" message, rather than pointing to a specific software bug within Android Auto itself. This means the issue could stem from hardware (cables, ports), software (app, phone OS, head unit firmware), or even configuration settings.

Common Causes

Before diving into solutions, let's understand the potential culprits:

Faulty USB Cable: The most frequent offender. Not all USB cables are created equal, especially for data transfer.
Dirty or Damaged USB Ports: On both your phone and the car's head unit.
Outdated Software: Android Auto app, phone's Android OS, or car's head unit firmware.
Corrupted App Data/Cache: Stale data within the Android Auto app on your phone.
Incorrect USB Connection Settings: How your phone handles USB connections (e.g., charging only vs. data transfer).
Device Conflicts: Sometimes other apps or settings interfere.

Troubleshooting Steps

Let's systematically work through potential fixes, starting with the simplest.

1. Check Your USB Cable

Replace the Cable: This is paramount. Use a high-quality, short (preferably less than 3 feet) USB-A to USB-C (or micro-USB) data cable. Many charging-only cables don't support the necessary data transfer rates. If possible, use the cable that came with your phone.
Inspect Ports: Look for lint, dirt, or damage in both your phone's USB port and the car's USB port. Use a can of compressed air or a non-metallic pick to gently clean them.

2. Restart Everything

Restart Your Phone: A simple reboot can often clear temporary software glitches.
Restart Your Car: Turn off your car, open and close the driver's door (to ensure the infotainment system fully shuts down), wait a minute, then restart.

3. Update Your Software

Android Auto App:
- Go to the Google Play Store on your phone.
- Search for "Android Auto."
- Ensure the app is updated to the latest version.
Phone's Android OS:
- Go to your phone's Settings > System > Software update.
- Install any pending updates.
Car's Head Unit Firmware:
- Consult your car's owner's manual or dealership for instructions on updating your infotainment system's firmware. This can often resolve compatibility issues.

4. Clear Android Auto App Cache and Data

On your phone, go to Settings > Apps & notifications > See all apps.
Find and tap on "Android Auto."
Tap Storage & cache.
First, tap Clear cache.
If the issue persists, go back and tap Clear storage (this will reset Android Auto, requiring re-setup).

5. Verify USB Connection Settings

Connect your phone to your car.
On your phone, pull down the notification shade.
Look for a notification related to USB connection (e.g., "Charging this device via USB").
Tap on it and ensure the setting is set to "File transfer / Android Auto" or "Transferring files" (not "Charging only").

6. Check Android Auto Permissions

On your phone, go to Settings > Apps & notifications > See all apps.
Find and tap on "Android Auto."
Tap Permissions and ensure all necessary permissions (Location, Microphone, Phone, SMS, Contacts, Calendar) are granted.

7. Try a Different USB Port (if available)

Some cars have multiple USB ports. Try connecting to a different one, as sometimes one port might be dedicated for charging while another is for data.

When All Else Fails

Factory Reset Android Auto Settings: On your car's head unit, look for an option to "Forget all Android Auto devices" or "Factory reset Android Auto settings."
Developer Options (Advanced):
- On your phone, enable Developer Options (tap Build number 7 times in About phone).
- In Developer Options, find Default USB configuration and set it to File Transfer or No data transfer. Experiment with these settings.
Contact Support: If you've exhausted all options, reach out to your car manufacturer's support or Google's Android Auto support.

By systematically working through these troubleshooting steps, you should be able to diagnose and resolve Android Auto Connection Error 21 and get back to enjoying a seamless in-car experience.