Low signal/"No service" on iPhone 3GS after upgrading to iOS 5.1

Hello,

After I upgraded my beloved iPhone (3GS) to the latest iOS version (5.1) I noticed that the signal on the phone is severely impaired and sometimes non-existing (showing "No service"). My phone worked fine until this upgrade.

Is anyone else experiencing the same issue?

Hi,
Exactly the same on my 3GS. Cellular signal strength has dropped by two bars and now continually drops out. Phone worked perfectly for last 12 months, in the same location, prior to upgrade.
Not happy.

Have you guys powered the phone off and on?

Err-really!

Rebooted a number of times.
Problem as stated.

I have:

- Rebooted phone several times
- Reset all settings
- Changed to a brand new SIM card

Problem still exists. I am very frustrated at the moment, nothing seems to help! Is there any way to downgrade to 5.0.1?

No more input to this problem?

Just fixed my low signal strength on iPhone 3GS after upgrading to IOS 5.1 - Hooray!

Phone has an older GSM SIM, and before upgrade had 3GS turned off in settings, with data also not enabled. I had 3 bars of signal strength and phone worked OK.
After upgrading phone only had one bar of signal, and alsointermittent service in the same location, often with "SOS calls" only displayed.
I tried turning "3GS" to "on" in settings, and to my surprise, 3 bars of signal strength returned, and now with stable service.
After the upgrade it appears that the 3GS slider now affects all signal strength.
Tried the same on an iPhone 4 with the same result.

Wife is happy again!

Where do you find this setting?

Settings\general\network\ then slide the "Enable 3G" slider to ON.

Seems like I don't have that slider in my iPhone

Strange, all the iPhones that I have seen, have the above.
Settings\General\Network\ then there are two slide switches. "Enable 3G" and another one "Cellular Data". Check to see if both, or at least "Enable 3G" is set to on.

Maybe you are in the wrong area.

Best of luck .

I was also getting no service when I upgraded my iPhone 3gs to 5.1 having baseband 6.15.00..even after i installed ultrasn0w..then i found this guide and my problem was solved..maybe you should give it a try

How to fix No Service on iPhone 3GS, iPhone 4 iOS 5.1