iMac late 2013 can't find nvme ssd after upgrade.

It seems like you've encountered a complex issue during your iMac upgrade. Let's troubleshoot step by step:

1. Hardware Connection:

- Recheck all hardware connections, especially the adapter for the NVMe SSD. Ensure that it's properly seated and connected.

2. Battery Connection:

- Since you disconnected the battery during the CPU upgrade, ensure it is securely reconnected. Sometimes, power issues can lead to problems.

3. PRAM and SMC Reset:

- Reset the PRAM and SMC. PRAM stores various settings, and SMC controls hardware functions. To reset PRAM, restart your Mac and hold down Command + Option + P + R until you hear the startup sound again. For SMC, shut down your Mac, hold down Shift + Control + Option + Power for 10 seconds, then release and power on.

4. NVMe SSD Compatibility:

- Verify that the NVMe SSD and its adapter are compatible with your late 2013 iMac. Check the manufacturer's documentation and compatibility list.

5. System Report:

- After connecting both SSDs, go to "About This Mac" > "System Report" > "NVMe Express." Confirm if the NVMe SSD is recognized. If not, it might be an adapter or compatibility issue.

6. Disk Utility:

- Open Disk Utility and see if the NVMe SSD is visible. If not, there might be a hardware or connection problem.

7. Boot Drive Order:

- Check the startup disk preferences in System Preferences > Startup Disk. Ensure the NVMe SSD is selected as the boot drive.

8. macOS Reinstallation:

- If the NVMe SSD is recognized, reinstall macOS on it. This might resolve any issues related to the operating system not recognizing the NVMe SSD.

9. Trim Enabler:

- If you've used third-party utilities like Trim Enabler, they might interfere with the system. Consider disabling such utilities and testing the system.

10. Check SATA SSD:

- Ensure that the SATA SSD is also recognized and properly seated. Check for any conflicts or issues with the SATA SSD that might affect the NVMe SSD.

11. Firmware/BIOS Update:

- Check if there are any firmware or BIOS updates available for your iMac that address compatibility issues with NVMe SSDs.

If the issue persists after these steps, it might be beneficial to seek assistance from Apple Support or a professional technician who can physically inspect the hardware and diagnose the problem more accurately.

Rencai wrote:

I haven't hear chime on the iMac. It looks strange.

When I press power button, the fan is on and disk is on(the hdd, I remove SATA sdd and plug SATA hdd again on iMac.).

Then the 2nd LED is on, but few seconds later(1 - 3) the 2nd LED is off.

Then the machine looks like restart, LED 2 is on again and Fan and Hard drive is working. No chime.

I don't know why, because I power off it normally and do not change any hardware except hard disk.

With this information, I would say you have either a problem with the power supply or the Logic Board. I don't know if the 2013 model has it, but I know on later models there is a short flat cable connecting the power supply to the Logic Board....this is not the power cable which connects to the back of the Logic Board & has a larger connector. On a later iMac I found the short flat cable to be bad which prevent LED #3 from lighting. If this cable exists on your iMac, make sure it is fully seated.

How I can test which place has problem when LED3 not on?

If your iMac has an integrated video card, then more than likely the Logic Board is bad. I saw a take apart guide and it appeared there was no separate video card on the 2013 model, but I could not be certain since I know some models have the video card mounted on the back of the Logic Board. If your iMac does indeed have a separate video card, then it may be bad, but you also cannot rule out a Logic Board problem. All we know is that the GPU & Logic Board are not communicating.

However, with the odd behavior you experienced with LED #2, it is hard to say for sure as that may confirm a Logic Board failure or possibly a power supply failure. These diagnostic LEDs are only a general guide, unfortunately to confirm requires testing with a known good part which is not really feasible. Keep in mind these diagnostic LEDs were meant to be an aid for certified Apple techs to use as a guide....these techs were able to order a test part from Apple to confirm which part is really bad. These diagnostic LEDs are not able to tell the exact part, only about where the failure may be.

For instance, I was using a repair guide from a 2010 iMac as a rough guideline to help figure out what else you could try (the meaning of the LEDs is the same). Unfortunately I was not able to find a repair guide for a 2013 model since Apple stopped publishing PDF service guides to their techs around that time so it is doubtful any copies can be found online. Probably wouldn't be of much use anyway since Apple assumes a tech can get access to a known good part for testing purposes.

I thought the PRAM coin battery was the simplest thing to try since I do know it can definitely prevent a computer (especially a Mac) from booting or powering on properly.

FYI, this is the reason most contributors on this forum advise against people opening up the iMac. It is possible something was left disconnected or not fully connected, or possibly something was accidentally damaged. There is even a possibility the new SSD or SSD adapter is causing a problem. Removing them & leaving the SSD slot empty would also be a good test since right now you need to get all the diagnostic LEDs lit, otherwise the SSD is meaningless anyway. There is even a possibility of a memory issue....maybe a memory module or memory "cage" is not fully latched in place (saw a reference to a memory issue as one of the troubleshooting steps if there is no startup chime), but there may be no startup chime until the LEDs are all lit (I don't recall as it has been a while since I worked on an iMac and I wasn't paying attention to when the startup chime occurred in relation to the diagnostics LEDs being lit).

Rencai wrote:

I have to recovery the system from internet again. Use command + option + R. But the recovery version is OS X 10.6.

Not possible for it to be 10.6 since 10.6 was only released on DVD. The oldest online macOS installer is 10.7 Lion. Unless Apple recently changed something anyway.

And can't detected Nvme ssd. I think Mac OS can support Nvme ssd after 10.13.

Correct. 10.13+

So, I use a USB drive to recovery the 10.15. (I made a use startup drive before I upgrade the hardware.) It also can't detected the Nvme ssd.

My guess it is the SSD adapter you are using to convert the M.2 SSD. From reading this forum for years, the best most reliable & compatible SSD adapter appears to Sintech. There is also a possibility the SSD is incompatible or faulty, but I would try the Sintech adapter first.

FYI, within Disk Utility click "View" and select "Show All Devices" so that the physical drives appear on the left pane of Disk Utility. macOS defaults to a volume view which can make it appear the physical drive is "missing", when only the volume on the drive is faulty or missing.

Edit: Try Command + Option + R to boot into Internet Recovery Mode to attempt to access the macOS 10.15 online installer. Unfortunately sometimes the Mac may still only boot to the oldest online installer available regardless of the keys used for booting.

Here is what the iMac's diagnostic LEDs represent:

https://logi.wiki/index.php/iMac_Logic_Board_LED_Indicators

Your condition means the Logic Board & GPU are not communicating. I believe the 2013 model uses an integrated GPU instead of a separate video card. If that is the case, then the Logic Board is likely bad.

However, try an SMC Reset & PRAM Reset (hold the PRAM Reset for at least three chimes).

There is a possibility the PRAM battery is bad. You could try removing the battery & trying to power on the iMac. The iMac should power on without the battery installed.

Do you hear a startup chime when powering on the iMac?