The phone charges. The screen stays blank. That specific combination — power but no CarPlay — points at one thing more often than anything else, and it is not the car.

Charge-only cables are the usual culprit

A USB cable can carry power without carrying data. Plenty of cheap cords are wired exactly that way, because leaving out the data lines makes them cheaper to build. They work perfectly as chargers and are completely useless for CarPlay, which needs a data connection to the head unit.

The giveaway is precisely the symptom above: the phone shows the charging indicator, and the car shows nothing. If it were a software fault the phone would usually not charge either, and if it were the port the phone would not charge at all.

There is no reliable way to tell by looking. The only practical test is to swap in a cable you know carries data — for example, one that has successfully moved photos to a computer.

The second cause: the wrong USB port

Many cars have several USB ports and only one of them is wired for data. The rest are charge-only by design, usually the ones in the rear or in the armrest. If your car has a port marked with a smartphone icon rather than a battery or lightning-bolt icon, that is the data one.

Try every port in the car before concluding anything.

Then check these, in order

1. Restrictions on the phone. On iPhone, CarPlay can be switched off entirely under Screen Time → Content & Privacy Restrictions → Allowed Apps. It gets toggled off by accident more often than you would expect.
2. Forget and re-pair. Settings → General → CarPlay → select the car → Forget This Car, then reconnect. This clears a corrupted pairing record.
3. Restart the head unit. Most cars need the ignition fully off and the driver's door opened and closed before the infotainment system actually power-cycles.
4. Update both. Phone OS and head unit firmware. Car firmware updates are usually a dealer or USB-stick job and are worth doing if the car is more than a couple of years old.

If it connects and then drops out while driving

Intermittent disconnection is a physical problem almost every time. A car cable gets plugged and unplugged daily and sits bent at a sharp angle against the console, so the wires just behind the connector fatigue and break one strand at a time. It works when parked and drops out over bumps.

The same applies to a worn port: if wiggling the cable causes the drop, the fault is mechanical, not software.

What to look for in a car cable

• Data-rated, not charge-only. Non-negotiable for wired CarPlay and Android Auto.
• The right connector. Most cars still use a rectangular USB-A port, so USB-A to USB-C is the safe default. Newer cars with a USB-C data port work with a USB-C to USB-C cable and an iPhone 15 or later.
• The right length. This matters more than people expect. A 6 ft cable in a car ends up looped around the gearshift or trapped in the centre console lid. If the port is on the console, roughly 1 ft is enough. If it is in the glovebox or under the armrest, 3.3 ft.
• A reinforced connector neck. That is where car cables fail, because that is where they bend.
• A spare. Cheap insurance against being without navigation on a trip, which is why we sell these in 2-packs.

See the CarPlay and Android Auto cables — both lengths, all data-rated.

CarPlay is a trademark of Apple Inc. Android Auto is a trademark of Google LLC. TOP-UP is not affiliated with either company.