Find my wrong location without WiFi

When you say, “My iPhone 18 Pro Max shows the wrong location in Find My when Wi-Fi is turned off. I only get an accurate location when connected to Wi-Fi,” I assume you mean that the location becomes inaccurate when the iPhone is relying solely on Cellular Data.

If that is the case, the first thing to investigate is the cellular network connection, rather than immediately assuming there is a problem with the iPhone’s location hardware.

Find My can determine a device’s location using multiple sources, including GPS, nearby Wi-Fi networks, cellular networks, and other available location information. When Wi-Fi is unavailable, the iPhone may rely more heavily on GPS and cellular-network information. If the cellular data connection is unstable, the device is having difficulty communicating with Apple’s services, or the cellular network is providing inaccurate or delayed positioning information, the location displayed in Find My may be temporarily incorrect or may show an older location.

There can also be situations where the iPhone is connected to a particular cellular tower whose coverage area is relatively large, or where the network's location information does not precisely correspond to your actual position. This can become more noticeable in areas with weak coverage, when moving between towers, or when the phone is switching between different cellular technologies or bands.

The fact that Find My shows your location accurately when Wi-Fi is enabled is an important clue. It suggests that the iPhone is capable of determining and reporting its location correctly, and therefore the problem may be related to the cellular connection, carrier network, or cellular data service, rather than necessarily being a GPS or hardware fault in the iPhone.

I would recommend checking the following:

• Make sure Location Services and Find My are enabled.
• Ensure Precise Location is enabled for Find My.
• Confirm that Cellular Data is enabled for Find My and related system services.
• Test the phone in another location to determine whether the problem occurs everywhere or only in a particular area.
• Check whether other Internet-dependent services work reliably over Cellular Data when Wi-Fi is switched off.
• Toggle Airplane Mode on and off to force the cellular connection to re-establish.
• If the problem persists, contact your cellular service provider and ask them to investigate the cellular data connection, network coverage, and location-related network services associated with your SIM/eSIM.

So, if the location is consistently accurate over Wi-Fi but becomes incorrect only when Wi-Fi is disabled and Cellular Data is being used, I would investigate the cellular network and carrier configuration first, rather than concluding that the iPhone itself is defective.