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2012 13” MacBook Pro with 500GB HSGT Hard Drive and 4GB of RAM (2GB+2GB) Hi All, Trying to help a friend with this MacBook. She tells me it was working, running 10.7. Then she tried to update it to 10.13 and then this machine no longer saw the hard drive. I could not get it to boot from internal hard drive but it would boot and run from an external USB drive I had. We figured the hard drive went bad. I suggested she buy a SSD (120GB) and more memory (and 8GB memory module, to give her 10GB) from Other World Computing. I put the new SSD and RAM in. Booted up in Recovery but get the “Error Code: DEC400” (which appears to be just a generic error). If I boot from external drive the computer runs fine, but Disk Utility can’t see the drive. I took the SSD back out and put it in the external enclosure OWC included with the order, and plugged it into my MacBook. Disk Utility even let me erase and format the drive with APFS. I connected the drive back to the 13” MacBook Pro’s USB port, and then used Recovery to install 10.14.1. Did that fine, and I set up the User Account. All seemed fine. But when I moved the SSD from the USB external enclosure back to inside the the MacBook it again could not see the drive. Got the flashing folder. Using Recovery I get the the DEC400 error again. I tried zapping the PRAM and did the SMC Refresh. Didn’t help. Anyone have thoughts of what is going on here? Thanks, Jeff
Your hard drive cable likely went bad. That’s why you see the flashing folder. Replacing it should help. MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable MacBook Pro 13" Unibody Mid 2012 Hard Drive Cable Replacement
