[Nexus 5 Q&A, Help & Troubleshooting] IvanKurnia:
*D821 (E) - hammerhead

*KTU84M

*HW version: rev_11

*bootloader version: HHZ11k

*baseband version: M8974A-2.0.50.1.13

*carrier info: NONE (is this wrong?)

*signing: production

*secure boot: enabled

*lock state: locked

#I didn't touch this phone's system, still original.

my story:

so it's been 3 weeks since I bought my phone. I was happy with it, nothing was wrong.

a week later, the 4.4.3 came out, I updated it, and nothing was wrong too.

until last night, I turned off my phone, curious to see how the Nexus 5's recovery look like,

I pressed (volume down + power), and I noticed that it enters FASTBOOT mode. and I just learned, navigate with the volume buttons and select with power button.

NOTICE: I'm already familiar with things like this, I was in the Galaxy W forum and Galaxy SIII mini forum. *yes lol I came from Samsuck

so I selected recovery mode and enter it.. I saw the android logo there, the healthy one, not the murdered robot with a red triangle on it.

I saw nothing but that logo, I pressed volume up button and the text showed up. I navigate down with volume down button, until it was down at the "wipe cache partition", I wanted to go up to reboot my phone, but I realized, the up button just a switch to hide or show the recovery text, so there's only one choice, press the power button, *if I press the power button, I wipe the cache because it selects "wipe cache partition"*.

and then it writes "wiping the cache", I was confused why it was so long, until I decided to reboot with holding the power button.

NOTICE: it is strange to wait sooooo long for cache wiping. I know this.

the system turned on. I'm not sure if the cache wiped cleanly, I'm afraid it will make the system error. so I decided to change my runtime from ART to Dalvik, so the cache wiped out and built again, strange process that took only 64 apps to optimize, that before it was around 110 apps. and then after reboot, I decided to go ART again to saw how many apps that optimized, LOL it was again, 64.

I reboot my phone again, and wait the reception, LOL strange I got no signal in my home *usually full*.

NOTICE: the signal has already gone after first cache wipe.

somehow I go to About Phone, Status on the Settings, and I found out the IMEI is UNKNOWN. I tried to check it with *#06# and it shows nothing.

I repeat the process how I get to the recovery and try to wipe cache, and it said, "error: can't mount /cache".

so I think the cache was gone?? I look to the "Explorer" app *the one who makes the root version too (Root Explorer)*, well the cache partition still there.. LOL

MY QUESTION:

1. am I having a defective Nexus 5? or there is a bug?

2. my IMEI lost, I have 2 expectations: my EFS/IMEI is truly lost, or the system just can't detect it? how can I know?

3. I saw a thread that tells me Nexus 5 doesn't have EFS partition backup, so where does the EFS located?

4. if I follow you guys, unlocking bootloader, rooting and etc. can I make my phone's state default again? *I don't mean fix this thing, just go default*

5. most important thing, HOW CAN I GET MY PHONE BACK TO NORMAL?? *peace bro

please help, right now I'm trying to reset my phone as soon as my backup finishes.

thx :)