update: i tried to turn on the computer after i failed to solve the issue, just for the sake of it, and i turned on! im currently writing this message on it, on the system information it says the correct 16 gb of ram installed, no errors showing up on the support assist app, this only goes to show how bizarre my issue is, as i did nothing to the computer and it decided it was able to turn on, with the 2 ram modules working perfectly. really hope someone knows what is going on as i was unable to find anything like it on the internet.

Hi @ZecaUrubu  welcome to this user to user forum. This is not Dell Support. 

The Alienware 15 R3 Diagnostics Light Pattern 2,3 = no memory or RAM detected. Swapping the RAM cards seems to have resulted in a temporary fix, but perhaps not a permanent solution.

Reseating the RAM cards is a well known solution. The system board gets dusty in normal use and the RAM card terminals and socket can collect dust. Remove the RAM cards, do not finger touch when cleaning the card terminals with a lint free cloth (no water, no solvents) to remove surface oxidation and/or dust. Also remove dust from RAM card socket using a lint free cloth (no water, no solvents), visually check with bright light that all dust and any cloth debris has been removed. Install RAM cards back into their sockets. This reseating process should give the permanent solution. 

Hi @ZecaUrubu  thank you for sharing update.

OK, perhaps BIOS is having problems detecting your RAM cards and a BIOS reset is required.
(1) Disconnect ac adapter.
(2) Remove rear cover.
(3) Disconnect main battery (do not remove).
(4) Disconnect (CMOS) disc battery (do not remove).
(5) Remove RAM cards and look for RTCRST (Real-Time Clock Reset) text, and their metallic spots on the system board. (6) Put flat screwdriver blade across RTCRST spots on system board.
(7) If there is no RTCRST, press and hold down the power button for one minute.
(8) Replace RAM cards, reconnect main battery and disc battery, replace rear cover.

Please share an update. Thank you. 

i already attempted to clean the sockets and the gold contacts on the ram cards, used a cotton swab with isopropyl alcohol, and it didnt seem to make a difference, ive checked it all with a light and it doesnt seem to have any debris or dust, but i will give it another shot, doing what you just said, but i doubt it will solve the problem.

Ok, @crimsom i tried to do as you told me, i removed the back cover, but i didnt remove anything else, i disconnected the cmos battery cable, i think, it was a bit hard to reach as there was a black plastic frame covering it, but i was able to disconnect the black and red cable (what im preety sure was the cmos battery cable, it was labelled RTC), then iremoved the ram cards and was not able to find the RTCRST spots on the board, again i didnt remove the black frame as i think the less i mess with the components the lesser chance there is that i create more problems, anyways i held down the power button for 1 minute, plugged everything back, and unfortunetely it didnt seem to make any difference Any other suggestions? 

Hi @ZecaUrubu  thank you for sharing a good update, that you have carefully undertaken a BIOS reset without damaging anything. However, did not fully understand your update post saying "unfortunetely it didnt seem to make any difference". Is your power button still giving 2 red 3 blue diagnostic code, or is there some other clue that there is a fault? The more faults you share with this forum, the better for other users to target the fix. 

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The Alienware models are different, so the Alienware 15 R3 user should visit their Dell Support Documentation, for example: Clearing CMOS settings, and the Alienware Support videos on YouTube, for example: How to Upgrade/Replace RAM, which shows the motherboard beneath the RAM card. 

RTCRST (Real-Time Clock Reset) becomes CLRP1 (Clear Pins No. 1) and this pair of pins are located beneath the RAM card, see image. Shorting these pins is undertaken by bridging with a metallic item.

Hi @ZecaUrubu  … other suggestions, you ask. The RAM card is very reliable, but your 15 R3 power button is still giving 2 red 3 blue diagnostic code. It is strange that the 15 R3 system detects all of your 16GB RAM (2 x 8GB) but remains unhappy. Booting on one of the RAM cards and then the other RAM card might reveal that one of the RAM cards, or the one of the RAM sockets has a minor fault, but still works. There are RAM diagnostic tests:- 

(1) If the 15 R3 does not boot, please tell the Dell F12 ePSA diagnostic to undertake a full memory test. This can take many hours. Hopefully this full RAM test will tell us more, when diagnostic finished, click on the bottom right hand corner of the screen to enter the full ePSA test results. Although the full RAM test might say pass, perhaps the root cause lies elsewhere, so have a good look and click on more information.

(2) If the 15 R3 boots, type memory into Search (bottom left hand corner of screen), click open and run the Windows Memory Diagnostic application.

These RAM diagnostic test results may give different information. If the 15 R3 boots, it may be prudent to run both diagnostic tests, to try and find this elusive RAM fault. 

Please share an update. Thank you. 

ok, @crimsom , when i said "it didnt make a difference" i meant as i still get the same 2, 3 pattern when i try to boot. After you sent the image of the pins i was able to find them. So i did as you told, i disconnected the AC, disconnected the RTC labelled cable, took the ram cards out and shorted the CLRP1 pins, then i booted the computer and after the computer tried to boot and turned off 2 times, the computer was able to boot directly into the bios and it asked for me to set the system time, so i set it and hit the "save changes and reset" button, but the when it booted again it gave me the same 2,3 pattern. i checked in the bios before resetting and it showed the full 16gb of memory avaliable. so this did not solve my problem, unfortunately

@crimsom sorry, i did not see your second reply before doing the previouly mentioned steps, the computer is currently not booting, so how do i "tell the Dell F12 ePSA diagnostic to run a full memory test"?

Hi @ZecaUrubu   thank you for sharing updates.

This conversation is being undertaken by sharing posts, so I cannot see what you see and I do not know the subsequent status of the 15 R3 having attempted a fix. Also do not know If you have undertaken a different fix based on your online research or conversation in another forum.

Having already undertaken a BIOS reset, further resets will not change the status of your 15 R3, unless the previous reset was ignored.

Having undertaken the RAM card swap around test, it seems that the RAM cards and their sockets do not have a fault.

To undertake the Dell SupportAssist F12 ePSA diagnostic full RAM test: Press and hold down the F12 key and then start the 15 R3. A menu will appear that looks something like the blue image previosly shared. Use the up and down keys to select Diagnostics and then press the enter key. A white Dell ePSA screen will appear asking if a test is wanted, and you say yes to get the test underway. When the standard ePSA test is completed, it will ask if a full memory test is wanted with the warning that this could take four hours. This time, you say yes, to get the full diagnostc test underway. After many hours, the white screen will then say the full memory test has been undertaken. Now look in the bottom right hand corner of the screen and click to enter the ePSA full test resuts menu.

Take time to read this paragraph before interacting with the full test results menu. On the left hand there are icons representing different parts of the 15 R3 system. If their ePSA test was a pass, they get a green tick pass. If the ePSA test was a fail, the icon gets a red cross fail. The top icon will say if all the connections are present, and you may have to scroll down to see the memory icon. On the right hand of the screen, it opens with a summary of the ePSA test results and you may have to scroll down to see all of the summary. If there is red text, it has found a fault, and you may want to use a camera to capture this information. Then click on the left hand icon to get the full ePSA test results for that part of your system, and you may want your camera to capture this information.

You are now ready to interact with the ePSA menu and capture an image of the fault that it has found. As this problem is elusive, the ePSA may say it has not found a fault.

As there is no thank you Kudos, please share an update so that another user may assist you. Thank you.

Hello @crimsom ! I just would like to mention that I currently have a similar issue with my 2017 15 R3, but in my case I get the light patterns: "2 red 3 blue" followed by some repetitive "3 red 1 blue". LEDs turn on and so does the laptop, but no screen image at all. Oh, and the fans...they go crazy until the laptop turns off by itself.
Some months ago I've replaced my RAM for a pair of 32GB modules (64GB total), which are the ones I am using now. They worked fine, until I decided to repaste the laptop. First repaste worked, but since temps persisted being high I tried once again the repaste and...lead to what it is now. No working laptop.

I've attempted to power up with the key combinations such as , , , as well tried shorting CLRP1 but, as mentioned, all I get is a black screen.
I understand from the light patterns that RAM is the first issue, but along also the CMOS battery. I tried replacing the CMOS battery, but it did not solve the problem. I now have again ordered new memory modules (should arrive in a few days), 16GB this time, as my last hope that the previous replacement modules somehow have failed.

Do you see any other possible troubleshooting that I could try out?

Thanks in advance!

Hi @Arthur Boss  thank you for sharing update. 

Alienware 15 R3 POST Diagnostics gives Light Pattern 2,3 = No memory or RAM detected, and 3,1 = CMOS battery failure. No screen image inhibits troubleshooting with F12 ePSA Diagnostics. 

Dell says the 15 R3 TOP SOLUTION (problem) is to Resolve No Power, No POST, No Boot or No Video issues with your Dell Computer This article is a guide to identifying and resolving start-up / power issues with your Dell PC. (These include No Power - No signs of life, No POST - Diagnostic LEDs or Beeps, No Boot - Can't load Operating System and No Video - PC starts but nothing seen on the display.) 

Getting the screen display to work is the top priority. The BIOS/UEFI tells POST the process to use, but BIOS function could be stuck, because of its battery or memory issue, and giving false positive so that POST is unable to complete (no splash window), and Boot into windows is inadvertently never started. 

Please press and hold down the D key, then press the power-on button, to enter the LCD built-in self-test (BIST). Continue to hold the D key, until you see colour bars on the LCD screen. If the LCD screen works, POST is giving false positive and preventing Boot into windows. Clear CMOS settings and install a new $10 CMOS BIOS battery cable assembly - Dell P/N 44YK6, or Dell P/N C8KT2. 

Please click on Kudos to say thank you for response from user that is not employed by Dell. Please share an update on progress, so that other users derive benefit from your experience. Thank you. 

Hello again @crimsom , and thank you so much for the reply!

I do have interesting updates to share.
I once again completely disassembled the laptop, down to the heatsink level, connected it to an external display and...it booted again!! I then proceeded to put everything back, but after putting on its frame/external covers, I came across the boot failure once again.
This leads me to think that there's something shorting the motherboard once I put in the cover screws (and for some reason that is reflected on an unrelated blinking code pattern), and I did try not tightening them too much, but I couldn't find the real reason yet so I can only suppose.

Nevertheless, I continue to troubleshoot the laptop without the covers, and then comes the interesting findings.

First, on my revival boot I saw warnings such as: "Unsupported video configuration detected"; "Real time clock error"; "System CMOS checksum bad", but then resetting the BIOS and updating the system time fixed these issues. I also proceeded to update my BIOS once I got back into the OS.

Now, onto testing and benchmarking...the performance is terrible!
I have the original 240W power adapter from Dell, and as I ran my benchmarks (I mostly use Unigine Heaven 4.0, but also some games) I could hear some clicking noises on the laptop's power jack region just as the laptop would request more and more energy. I couldn't differentiate if the noise was coming from the power supply or the laptop. For this reason I connected the power supply in a different outlet, and now I do not hear the noise anymore. Still, I am 100% sure the issue does not lie on the outlet. The noise went away, but not all problems...
Checking the temperatures, the GPU does not cross the barrier of 93°C, but the CPU goes up to 100°C. I tried undervolting the CPU a bit to see if there would be a difference in temperatures, but they did not decrease.
Thing is, I have huge FPS drops...they variate a lot. And the results of my benchmarks are basically half less than the scores I had before all these issues. In Unigine Heaven (set to FHD extreme settings), I previously had an average of 84.3+FPS and now it will not surpass 45FPS.
I then noticed the most important detail: along with the FPS, the GPU clocks are fluctuating immensely. The GPU is a GTX1070, and its clock goes from around 1440 MHz down to 200 MHz (???). I have never seen such a gap in clock numbers.
For these tests, I used different versions of Windows 10, Linux Ubuntu, as well as different versions of Nvidia Drivers on them. The problem persist across OS's.
I just ran a thorough test on Dell's pre-boot diagnose tool, but it does not point out any issues there.

Honestly, I am really concerned of why this GPU issue is happening and now I ran out of ideas on how to fix this. I hoped it could have been a software issue after all, but it is definitely not.

I shared my findings in the hope that if someone goes through the same boot issues I had, at least manages to boot back into the system just as I did. Sadly though, I have other issues now. If there's any ideas on why this is happening, please share with me. I am already thankful for your reply and hope you can share some more knowledge!

I say that maybe the heat sink was installed wrong. Did you do the cross screw method where you do top left and bottom right then top right then bottom left? Also did you put some high quality thermal paste and thermal pads that absorb a lot of heat? And finally, did you clean the heat sinks well because sometimes the insides have dust in them. I also say for the case shorting the motherboard, try looking at areas where metal touches the motherboard in a away that causes it to short I.e like a mount touching a circuit instead of the mounting hole.

hello @Alienware Area-51 ALX 2006 !

Yes, I did follow the screw index order found on top of the heatsink. I applied a high-quality thermal paste (although I forgot the name of it now) and replaced the thermal pads with new Thermal Grizzly ones. All dust has been removed and everything is shiny clean.

Things is...thermal throttling was how it all started. I am sure you've seen thermal throttling is a common issue with the Alienware 15 R3, but I just feel like my luck has been a bit worse with this machine, so repasting was the reason I opened up my laptop at first.
By the issues I am have now, I am assuming the laptop still suffers from thermal throttling and repasting did not to it. It's just that I have never seen it reaching such a level of performance loss and fluctuating clocks like it is now, when it was supposed to be better.

I kinda believe that the the heatsink is not touching the GPU and CPU properly, as when I removed it, somehow the contact surface of the heatsink lost a bit of its copper and turned into a grayish colour, like it has been used enough. The heatsink is the original one and it seems to sit perfectly in place, but sadly I cannot see if it is indeed touching the Processing Units or not.

Opening up Intel XTU's software, I did see it pointing out power limit throttling constantly, and less but yet frequently, thermal throttling. Cannot say I get what power limit throttling means, but I did end up ordering another power supply to test out the system (but again, the same happens when I'm on battery, so I am doing it just to mark this one out of my possibilities list).