Alienware 15 R3 Service Manual says that a 2,3 pattern indicates a "No memory or RAM detected".

1. Unplug the AC adapter.
2. Remove the base cover
3. Disconnect the battery
4. Press and hold the power button for 30 seconds to discharge residual power.
5. Remove the RAM sticks.

6. Use a soft pencil eraser to clean all the contacts on the RAM stick. 

7. Moisten a microfibre cloth with 99% isopropyl alcohol and use a credit card to slip the damp cloth into the RAM slot to clean its contacts.

8. After everything is dry, insert one RAM stick firmly at a 30° to 45° angle, ensuring that it seats fully in the slot.

9. Connect the AC adapter.

10. Try to boot into BIOS to see if the RAM is recognized.

11. If that works, again disconnect AC adapter, press and hold the power button for 30 seconds to discharge residual power.
12. Remove that RAM stick and insert it into the other slot.

13. Connect the AC adapter.

14. Try to boot into BIOS to see if the RAM is recognized.

15. If that RAM stick works in either slot, now repeat the entire process to test the other RAM stick in both slots.

The goal is to narrow down if the problem is one RAM stick, one RAM slot, or something more.

Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard.

Hi @orang welcome to this free user-to-user Alienware laptop discussion forum. 

Alienware 15 R3 Diagnostics | Dell US says 2 red, 3 blue = No memory or RAM detected.  

DDR4 memory cards are very reliable and rarely fail. Please clean copper connection with lint free cloth (no water, no solvents) and reseat the DDR4 memory cards in their slots. Alienware 15 R3 Replace memory modules - Procedure | Dell US. NOTE: If you do not hear the click, remove the memory module and reinstall it.  

Hello, I am not sure how to disconnect the battery. It would be best if you would tell me. Thanks

It's in the Service Manual that I linked in my first post. Here is a link to the procedure for removing the battery.

Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard.

I attempted to boot up the computer but it still gives me the usual 2 red 3 blue code. Could you please help?

Did you do all four tests as I described, one stick at a time? (stick 1 in slot A, stick 1 in slot B, stick 2 in slot A, stick 2 in slot B)

If you performed all four tests and continue to see only the LED 2.3 sequence, then that may indicate a more serious motherboard failure.

To be sure, if you are able, you could get some RAM that you know to be good and test it in your laptop. You could also test your RAM in another laptop.

I have done all 4 tests that you have described and it still gave me the 2.3 blink code. Im not sure what is happening as whenever I let the computer rest for a day it boots up fine the next day. It might be a motherboard issue, i’m not sure though. 

If you could get some RAM that you know to be good and test it in your laptop, that would be useful. You could also test your RAM in another laptop, which would tell us if that RAM is okay.

I suspect you have a motherboard issue, though it's odd if you say that sometimes it runs okay.

Hi @orang thank you for sharing that issue is intermittent. 

Please create system restore point, you may have to enable this feature. How to use System Restore on Windows 10 | Windows Central.  

Please run Check Disk to automatically look for and fix window file errors. Open This PC, right click on OS (C:) drive icon, open Properties - Tools tab and run Error Checking, click on Scan drive. How to Use the Chkdsk Command in Windows (lifewire.com).  

Please run windows Reliability Monitor to see if system will reveal the root cause of this issue.  How to use Windows Reliability Monitor to identify software issues | Dell US.