You're right, the Z87-A doesn't feature the Q-Code LED's able to display the code as a numerical value (other models like the Z87-WS have them).
So you're pretty much stuck with the four on/off LED's spread around the board.
Anyway, the CPU_LED being lit means the CPU couldn't start during the boot process. This could indicate one of the following problems:
- defective or not properly mounted CPU
- defective PSU
- short-circuited motherboard or component attached to the motherboard
But since you wrote that other components are powering up just fine, my guess is it's a defective CPU.
Regarding the warranty, someone from Intel would have to answer that.
Thank you for contacting the Intel Communities.
I would like to provide you with some troubleshooting that could be performed in your system.
1. Test the system without RAM, you should receive 3 beeps in the power button, no video will be present.
2. Test your RAM modules separately on each DIMM slot.
3. Are you able to access the BIOS?
4. Also check that all the connections are properly set. (HDMI, power adapter, RAM, SSD, etc.
5. Test the system without any additional components, if it works, add one component at a time in order to check if one of them is the problem.
6. Test a different power supply if doable.
7. If possible, test your board with a different CPU.
If after performing those steps, the problem persists, chances are that this is a bad CPU.
You can get in touch with Intel Customer Support at Contact Support to get warranty support.
If you require any further information or support, do not hesitate to contact us back.