iPhone 17 Pro Max poor data connection compared to iPhone 15

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iPhone 17 Pro Max poor data connection compared to iPhone 15

My iPhone 17 Pro Max has poor data connection. Using the Field Test Mode (dialling *3001#12345#* in the phone app) reveals that the SINR values are between -30db and -20db which I understand is really bad. Compared to an iPhone 15, which has SINR of about +10db to +20db. So clearly there’s either a problem with my iPhone 17 Pro Max individual device, or the iPhone 17 Pro Max design in general.

I’ve tried getting the device replaced by Apple, which they have offered to do as they say it’s not right. But annoyingly they won’t send out the replacement device until days/weeks after receiving mine, and I need the phone every day to manage and monitor my health, which Apple Support care nothing about.

I’m wondering if my particular device is faulty, or whether all 17 Pro Max’s are equally bad.

Anybody else having a similar issue with data connection on the iPhone 17 Pro Max?

iPhone 17 Pro Max, iOS 26

Posted on Oct 15, 2025 12:32 PM

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Answer 1

JimR123 Author

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Oct 15, 2025 1:20 PM in response to Jeff Donald

Not quite the same numbers as I quoted above as didn’t get screenshots of those, but here’s when I did another test with the same O2 physical SIM card, testing it in both the 15 and 17 Pro Max. Indoors this time.

15 with much higher SINR numbers, which was reflected in the ability to use the internet when WiFi was disabled, whereas 17PM could not use internet without WiFi.

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Answer 2

Jeff Donald

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Oct 15, 2025 12:49 PM in response to JimR123

Please post a screenshot of the dashboard from both devices.

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Answer 3

JimR123 Author

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Oct 15, 2025 3:05 PM in response to Jeff Donald

I’m in the UK. I’m not choosing the bands to test. That’s just what the phones chose for themselves.

But I have seen it where both phones have been on the same band and bandwidth and the SINR numbers are similar to above (15 ok, 17PM bad)

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Answer 4

Jeff Donald

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Oct 15, 2025 5:03 PM in response to JimR123

The split bars still indicate weak signal, which is substantiated by your Field Test. They can also indicate it may be roaming. But the test isn’t the same between the two devices.

Are both devices on and next to each other when testing? Have you tested 5G and if so what do the field tests show. Have you run the Speed Test app or equivalent in UK? If so do you have screenshots?

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Answer 5

Jeff Donald

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Oct 15, 2025 1:51 PM in response to JimR123

Look at the broken bars on the signal strength meter on 17 PM. Broken bars mean there is a weak or unstable cellular signal, or that the phone could be in a state of searching or trying to connect to the network. The dashed or broken bars visually communicate that the signal quality is not fully solid or consistent.

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Answer 6

JimR123 Author

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Oct 15, 2025 2:56 PM in response to Jeff Donald

The split bars are because in the 17 Pro Max I have 2 SIMs. A physical SIM for O2 network and an eSIM for EE network.

I originally had just the EE eSIM, noticed the problem so added the O2 SIM to see if it was a problem just with EE. Both give similar results.

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Answer 7

Jeff Donald

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Oct 15, 2025 2:22 PM in response to iPhone11mike

Let’s see the screenshots please.

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Answer 8

Oct 15, 2025 1:50 PM in response to Jeff Donald

I have an IPhone 17 pro and I am having the same poor network issues. I live in the United States and travel monthly for work. No matter what state or city I go the network issues slow and drops a lot. I also swapped from LTE to 5g on to 5g auto. Apple should let you downgrade phones because this issue have been a pain because I need my phone to be reliable.

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Answer 9

JimR123 Author

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Oct 15, 2025 3:00 PM in response to iPhone11mike

I have considered downgrading but I need the better cameras on the Pro models. It’s very frustrating that the Pro models with better specs seem to have worse connectivity than the base models. I’d expect the most expensive models to be the best at everything.

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Answer 10

Jeff Donald

Level 8

43,164 points

Oct 15, 2025 1:46 PM in response to JimR123

What country are you in? Why aren’t you testing 5G instead of LTE? You’re also testing different bands.

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