[Galaxy S 4 Q&A, Help & Troubleshooting] Camicia:
So this is my attempt to give back to the huge amount of help I received on this forum

TL;DR:

After a few different kind of attempts, this fixed the problem for me: the reflow of the SIM connector and the IC described at http://forum.gsmhosting.com/vbb/f25...already-change-sim-reader-1780363/index2.html . There are a few different things that can cause the NO Sim Card and SIM Card removed problems. In my case it did not start happening after events like upgrades or changing the firmware. It was also initially happening only once or twice a week.

Long story:

I have a T-Mobile Samsung Galaxy S4 (SGH-M919). I started having problem with the "SIM card removed" once or twice a week. It was a little annoying and I read about it online. Tried a few software solutions but they did not work.

I read somewhere to try to replace the SIM card and that is what I did. That made things worse... after T-Mobile replaced the card I start having the "no sim card" problem. At the T-mobile store they told me that I would have to send the phone in for a repair... well, out of warranty changing the motherboard could be $300 that is more than how much you pay for the whole phone used on eBay... I asked to restore my old SIM card but the person there told me that they cannot do it :crying: :crying: :crying:

After a little bit of cleaning the new SIM, plug it out and in a few times, the phone actually started recognizing the SIM card but it took only a few minutes before I got the "SIM card removed" modal on the phone =/ The problem just got a lot worse and it was happening every other hour...

Apparently if you read online there are a few things that can cause these errors. Only one seems to be software and it happen on SIM cards that have a pin when you update to Android 4.4.2 (I think) and it was fixed on 4.4.4. You usually know why this happen because you just run an update. If this is the case for you, I would try to work on the ROM/modem firmware. Otherwise it is probably a hardware problem.

There definitely may be different problems that create the SIM card error. You never know. The faster solution is replace the mainboard. Apparently there are people that write in the forums that even this did not work for them.... not sure what the cause of the problem can be there.... it is quite weird.

I spend a lot of time reading here on XDA and other forums. I finally started doubting that it was a software problem and eventually landed on this video: https://www.youtube.com/watch?v=OHQaQVLV1U8 - I bought a new SIM/SD card reader on ebay for $7 shipped. I replaced it in the phone. You need to be careful but if you have good sight and some basic phone repair tools, you can do it. I tested before reassembly of the phone. It works :D ! I reassembled and I got again the "No SIM card" problem :crying:. So I just wasted my time and $7 with no improvement. I read somewhere about a guy that fixed the problem putting duck tape on the SIM connector. It was a problem with a component not fully attached, it may actually work. I tried to put a 3 layer of little rectangular pieces of painters tape on the connector. That helped a lot. I was never getting "NO SIM card" but every now and then I was still getting the "SIM CARD removed" modal. I suspected that since that extra pressure on the connector was improving the situation, the problem could have been that the connector on the motherboard was not solder properly anymore.

I eventually found these 2 threads:

http://xdaforums.com/showthread.php?t=2375982&page=23 (on page 23 there is a guy that talk about re-heating this chip) and http://forum.gsmhosting.com/vbb/f25...already-change-sim-reader-1780363/index2.html (on the second page there is a guy that talk about reflow of an IC).

Anyway, I went to one of the local co-working spaces that has soldering stations with hot guns etc. I solder in the past but in these days phones have extremely small SMD components and it is extremely easy to mess everything up. So unless you are or you know somebody that is very good at soldering, do not do it.

I found a guy there that was willing to help. We prep the board with aluminum tape so we could protect the other components. Only the IC and the SIM connectors were exposed. We did reheat once with the hot gun with low airflow and 300 degree celsius spending less than 10 seconds on the board. It seemed that worked but after 1h I got the "SIM card removed" modal again :( The whole disassembly + preparation is a pain in the neck but I did it again. We reheated again spending a little bit more time on the IC (20 sec) and a little more on the SIM connector on the board (after shielding the IC). After cleaning some residue of glue left by the aluminum tape, I tested again. So far it is working. Fingers crossed!