Erratic Cellular Signal on iPhone 12

Question

Level 1

36 points

Erratic Cellular Signal on iPhone 12

I have been having lots of issues for a very long time. I have had my phone checked at a Genius Bar, talked to both Apple and Telus several times, Google for help with my issues, none of which helped.

Most of the time I only get 1 bar of signal even though I am surrounded by cell towers at my house. Gee, I even see the tower red light blinking at night from my windows. It's about 1 km away.

But, sometimes, especially upon rebooting the phone, I will get 4 bars, or if I force it to use only LTE. Right now, my phone is not even telling me if I'm still on LTE or 5G. No indicative icon showed next to the cellular signal icon at the top right of the screen.

Also, although it may not be related, sometimes the people I call cannot hear me properly. Is it caused by an unstable signal??? I also have consulted Telus and Apple on this issue, with no resolution thus far. I'm totally in the dark. It's like being in a nightmare with no way out.

Any ideas?

-Ron

iPhone 12, iOS 18

Posted on Sep 8, 2025 10:57 PM

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Answer 1

Alancito

Level 7

30,402 points

Sep 8, 2025 11:04 PM in response to SSL-ADT

Ron ~ As your iPhone 12 could be 5 years old, it's worth checking for a weak, aging battery which can cause connectivity issues. So...

Does your iPhone 12 still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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Answer 2

Alancito

Level 7

30,402 points

Sep 8, 2025 11:44 PM in response to SSL-ADT

SSL-ADT wrote: Original battery with a maximum capacity of only 82%."

Ron ~ 82% is close to the 80% level at which Apple suggests having the battery replaced. And that original old battery is probably no longer supplying sufficient power to the iPhone's antenna to connect properly with cell tower signals. So have the weak, aging battery replaced and all will be well:

iPhone Battery Service

About genuine iPhone batteries

Repair Provider Verification

(Articles found by searching Apple's Knowledge Base.)

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Answer 3

Alancito

Level 7

30,402 points

Sep 9, 2025 9:07 AM in response to SSL-ADT

SSL-ADT wrote: "in that case, why is the issue only sporadic?"

Ron ~ Because a weak, unhealthy battery "with a maximum capacity of only 82%" can cause intermittent voltage/current shortfalls and dynamic power management to kick in — so connectivity issues will often be sporadic rather than constant.

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Answer 4

SravanKrA

Level 10

433,100 points

Sep 9, 2025 8:04 AM in response to SSL-ADT

Please check the bandwidth that you are getting. Disable WiFi before running this Field Test.

You may check the current LTE band/5G/4G/3G by dialing *3001#12345#* pressing the call button and then selecting the Serving cell info option

Bandwidth on the 2nd and 3rd Screenshots.

See the pic below which is self-explanatory

E, 2G, 3G, 4G, LTE, VoLTE, and 5G all are Carrier Specific features. Contact your Carrier (Cellular Service Provider), the agency that issued the SIM / eSIM to you. About the LTE options on your iPhone - Apple Support (IN)

See the Pic below and the explanations thereof

The pic below is self-explanatory

However, iPhone model-specific feature is listed here --> Identify your iPhone model - Apple Support . and tap on "See the Technical Specs for Model "XXXXXX" under each model and Scroll down to the "Cellular and Wireless" section.

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Answer 5

SSL-ADT Author

Level 1

36 points

Sep 8, 2025 11:14 PM in response to Alancito

Original battery with a maximum capacity of only 82%.

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Answer 6

Alancito

Level 7

30,402 points

Sep 10, 2025 3:15 AM in response to SSL-ADT

SSL-ADT wrote: "...I bought mine in 2023, but it was a refurbished phone that I got from Koodo."

Ron ~ "refurbished" means it's not the "Original battery" as you previously stated. So verify that Koodo is listed here:

Repair Provider Verification - Official Apple Support

...and then check your iPhone was refurbished with a genuine Apple battery:

About iPhone Parts and Service History - Apple Support

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Answer 7

SSL-ADT Author

Level 1

36 points

Sep 9, 2025 7:59 AM in response to Alancito

in that case, why is the issue only sporadic?

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Answer 8

SravanKrA

Level 10

433,100 points

Sep 9, 2025 8:06 AM in response to Alancito

I have an iPhone 12 Pro, bought in February 2021, that is still running without any issues in India.

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Answer 9

SSL-ADT Author

Level 1

36 points

Sep 9, 2025 12:58 PM in response to Alancito

I have to admit, my iPhone (AKA iFun) battery does not hold charge for very long, it seems. I have better luck with my MacBook Pro.

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Answer 10

SSL-ADT Author

Level 1

36 points

Sep 9, 2025 2:25 PM in response to SravanKrA

Thanks for the thorough info, but I am in Canada with Telus, and the Serving Cell info you are referring to doesn't seem available to me.

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Answer 11

SSL-ADT Author

Level 1

36 points

Sep 9, 2025 7:55 PM in response to SravanKrA

I suspect it is because it is warmer in India. I bought mine in 2023, but it was a refurbished phone that I got from Koodo.

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Answer 12

SSL-ADT Author

Level 1

36 points

Sep 10, 2025 5:28 AM in response to Alancito

In the About page, I see absolutely nothing about any parts. The repair provider verification page seems to be only for the U.S.A.. Koodo is owned and operated by Telus, the head company.

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