[T-Mobile Samsung Galaxy S 4] filter4ever:
Since this has been an issue for me for a LONG time, and Samsung as well as carriers aren't clear on a repair - I'm going to explain what all I did to fix it.

It started over a year ago. I was waiting on a friend to contact me that came all the way up from Portland. Waiting all day, I went to give her a call and it said "No SIM card detected, please reboot to detect your SIM card". Rebooted, gave her a call and found out she was trying to get a hold of me all day and had to head back. I can understand how frustrating this can be for anyone.

There are MANY factors that can cause this, which is why this issue hasn't been completely resolved by Samsung. These factors include:

* The SIM itself

* The SIM slot

* The connector that connects the SIM / SD holder to the motherboard

* The motherboard

* The firmware

It will take some trial-and-error to find out what will work, but the first thing you can try is cleaning your SIM / Slot contacts with a piece of paper and a cleaner of your choice (I use QD electronic cleaner, and a piece of paper). After cleaning, reinstall and wipe the cache. This worked for a while.

I looked at the SIM contacts after replacing the holder. These contacts on the S4, at least my original holder, are VERY flimsy, and even just applying downward force (with a pencil eraser or your finger) to get a grip on the SIM to pull it out can throw them out of alignment. I suggest using needle-nose pliers or tweezers to GENTLY grip the SIM (by the side), after first unlatching the SIM (Push Forward).

What finally worked for me is replacing the SIM slot (for the 6th time) and the SIM card. There are actually many different versions of the SIM and SIM slot, so here's the versions that worked for me (T-Mobile customer)

[IMG="SGH-M919 SIM and SD Slot"]http://i.ebayimg.com/images/g/A0EAAOSwx6pYq7r-/s-l1600.jpg[/IMG]

The version is to the top-right of the SIM holder. This is the one that worked for me, or "I9505 R0.3" Also note that the bottom right of the SIM slot itself has the mark "TE" for "TE Electronics" or "Tyco Electronics". If you have heard of Tyco (Electronics - not toy company), they are a major player. TE Electronics makes high quality parts for harsh environments. This brand mark is a good bet you have quality contacts for your new SIM. Here is where I bought it: http://www.ebay.com/itm/171514317032

After installing it, it did not work yet. It worked with every other provider BUT T-Mobile. Seeing as though this is a T-Mobile phone, I called them to see what was up. It was not blacklisted, so they sent me a new SIM card for free (since I paid for one that didn't work). Popped the new one they shipped me in, and it works!

There are MANY different kinds of SIM cards. Different carriers, different manufacturers, different versions, thickness, size of the contacts, are just a few of the factors that can be an issue with the SIM itself. A T-Mobile SIM has it's version on the back of the SIM, near the ICCID (SIM Number). Mine is the "Universal" Mini/Micro/Nano SIM, version: TM9260 06.00.

After installing, I wiped the cache partition, for good measure. BAM! Works!

This issue has been frustrating for me for a while. I hope this helps. If it does, please reply and/or share. I'm not looking for credit, I just am trying to narrow down all the factors and troubleshoot what is the actual issue. Good luck! :cool: