With rapid product development cycles, software bugs are a constant headache for tech companies today.
Despite Apple’s stellar reputation, their products are not immune to such challenges.
Most recently, users reported getting pop-ups telling them “only one accessory can be used at a time” when trying to connect to Apple CarPlay.
To resolve the “only one accessory can be used at a time” issue in CarPlay, navigate to face ID & passcode in the CarPlay settings. Scroll to the USB accessories and allow access to any accessories you wish to add. If that doesn’t work, a hard reset may also be required.
For many iPhone users, there appears to be a frustrating randomness to the way the issue arises and subsides.
I’ll discuss the matter in greater detail in the following sections.
Resolving the “Only One Accessory Can Be Used at a Time” Error
Sometimes, CarPlay can refuse to connect to an iPhone plugged in via the lightning-to-USB cable.
If you’re seeing the “Only One Accessory Can Be Used at a Time” error message when trying to connect to CarPlay, chances are you will not be able to use CarPlay at all.
Understandably, this can be a very frustrating experience!
This particular error seems to be an issue for iPhone users who switch between connecting to CarPlay wirelessly and through a USB cable.
It may be arising because CarPlay is still attempting to connect wirelessly, even as you attempt to connect via cable.
While Apple has mostly remained quiet on the issue, two known ways exist to resolve this problem, even if only temporarily.
1. Force Restart Your iPhone
Many iPhone users clear this error message after resetting their phone. Here’s how to do a hard restart:
- Hold down and release the raise volume button.
- Hold down and release the lower volume button.
- Hold down the side lock-button until the Apple logo reappears.
This solution often works for newer iPhone models, but the restart process is slightly different if your phone is older than the iPhone X.
Keep in mind that this is not a factory reset, so you will not lose saved information, settings, and data.
Watch this video if you’re still confused:
2. Change USB Accessory Settings
Apple’s iOS 11.4.1 introduced a security feature that limits access to your iPhone through the lightning port under certain conditions.
The company didn’t really advertise the feature, so many iPhone users aren’t aware of it.
Basically, there’s a USB accessory setting on the iPhone that, when disabled, will block USB accessories from connecting to your phone when it has been locked for over an hour.
Why? Many hackers and law enforcement officials possess tools that plug into your lightning port, allowing them to circumvent passcodes and access sensitive information.
The USB accessory setting protects your phone if you leave it unattended or lose it, or if it falls into the hands of intrusive law enforcement or forensics agencies.
Here’s how to change this setting:
- Go to the settings tab on your iPhone’s menu.
- Navigate to Face ID & Passcode.
- Scroll to USB Accessories.
- Flip this setting to “on” (it should turn green).
Watch this GIF to see:
Many users find that changing the USB accessory settings fixes the issue, but you may still need to reset your phone on top of this.
Remember that turning the USB accessory setting on allows accessories to connect and interact with your phone in ways beyond charging.
This enables CarPlay, but while CarPlay is harmless, not every USB accessory will be.
3. Contact Apple Support
Unfortunately, you may also get an “Only One Accessory Can be Used at a Time” error if you have a serious issue with your iPhone.
In this case, restarting your car or infotainment system won’t work, and it may be time to contact Apple’s support team.
That said, the problem seems to be random for many users, and your phone may connect to CarPlay after failing many times in a row.
So, keep trying to connect before you consider more drastic measures, such as replacing a phone.
Final Thoughts
Whether it’s an unfixed software bug or an adverse effect of some internal security measure, the “only one accessory can be used at a time” error is nonetheless frustrating.
Many iPhone users successfully connect to CarPlay after changing their USB accessory settings and/or resetting their phone.
Doing either of these things may work, but you may also find that the issue recurs.
If this is the case, you can contact Apple support or wait until Apple explicitly addresses this in a CarPlay software update.
