Mojave install issue on Late 2013 iMac 27"

[macuser453787]

Hi all,

I've been running into an issue attempting to install Mojave on a late 2013 iMac 27", currently running High Sierra 10.13.6, firmware v146.0.0.0.0, internal drive is a 2TB spinning HDD (and most of that disk space is not used, if anyone is wondering). IIRC, it has 16GB RAM.

The installer runs briefly and then returns the error saying it can't install the OS due to an error verifying the firmware. I tried several times, including once after resetting the NVRAM as one post suggested trying.

I've seen a few posts discussing this issue but none seem to be applicable to this situation except for this post, where repairing the firmware is discussed (see post #10):

Firmware error with High Sierra?!

Hey Guys, I tried upgrading my mac to High Sierra and I am getting this error. Any suggestions on what may be the cause? I am running Sierra right now.

forums.macrumors.com

The above thread is about a similar issue when trying to update to High Sierra, but could the same solution from post #10 apply here?

Or do you have any suggestions otherwise?

Any help is greatly appreciated. Thanks!

 

[davidlv]

Hi all,

I've been running into an issue attempting to install Mojave on a late 2013 iMac 27", currently running High Sierra 10.13.6, firmware v146.0.0.0.0, internal drive is a 2TB spinning HDD (and most of that disk space is not used, if anyone is wondering). IIRC, it has 16GB RAM.

The installer runs briefly and then returns the error saying it can't install the OS due to an error verifying the firmware. I tried several times, including once after resetting the NVRAM as one post suggested trying.

I've seen a few posts discussing this issue but none seem to be applicable to this situation except for this post, where repairing the firmware is discussed (see post #10):

Firmware error with High Sierra?!

Hey Guys, I tried upgrading my mac to High Sierra and I am getting this error. Any suggestions on what may be the cause? I am running Sierra right now.

forums.macrumors.com

The above thread is about a similar issue when trying to update to High Sierra, but could the same solution from post #10 apply here?

Or do you have any suggestions otherwise?

Any help is greatly appreciated. Thanks!

I have a 2012 27" iMac, older than yours but essentially the same.
I cannot find that "firmware" version anywhere, are you sure it is not the "Boot ROM Version"? (mine shows 421.0.0.0.0)" That is shown in the Apple Menu/About this Mac/System report.
In any case try that method listed in Post #10 on the link you posted.
Then report back here.

 

[Racineur]

I have a 2012 27 iMac, 1 t FusionDrive. It came with Mountain Lion. Try this if you wish. I never upgraded ML. Still there and still useful at times (yeah yeah). I have 4 external SSD with Sierra, High Sierra, Mojave and Catalina on each and I can boot in any version of these macOS. I mean: boot. Not change on the fly. I decided that the best OS for a i5 3.2 HGz is Mojave. Updated and trouble free. I'll keep this old machine until it dies. Gaining 20 seconds to treat a photo is no big deal to me. But I must say, the new colourful 24 got my attention.