Dead ethernet port?

in the future please begin a new post as your issue may not be identical in solution and it can get confusing to the OP.

try deleting the Ethernet service

>System Preferences/Network

use your administrative credentials to unlock the panel if you need to

select Ethernet, click the "-" to delete the service

Shut down

Disconnect all external devices except OEM mouse and keyboard

reset the smc

https://support.apple.com/en-us/HT201295

reset the NVRAM

How to reset NVRAM on your Mac - Apple Support

then boot into safe mode

https://support.apple.com/en-us/HT201262

then reboot normally with devices disconnected.

then go back into

>System Preferences/Network

use your administrative credentials to unlock the panel if you need to

click the "+"

add Ethernet and configure

Hi, I have the dead ethernet port problem as well. I've had 4 ISP techs come out to connect my iMac 2009 ethernet and no go. Only after calling Apple was I told the port was dead after running ipconfig and testing the connection. There was no light on the router. When a PC notebook was used, using the same cable, there was a light on the modem. I updated the OS this weekend but the problem has been going on since we moved into a new house 8 months ago. At the apartment my iMac ethernet worked fine. It is too convenient that when I switch ISP's the port all of a sudden doesn't work. I'll take the iMac to the apartment and try it there again. I'm thinking its a OS problem or a ISP networking problem. I don't believe this port is dead conclusion. What tests can I run? I'm running TechTools Pro 8 now but I didn't see any ethernet port test info anywhere. I've already swapped cables and used the Network wizard to no avail. Wifi is up and running no problem. Any directions would be helpful. TIA

Hi Jimmy,

Thanks for the instructions. I followed them and I'm waiting for the router perimeters from the ISP.

I have noticed another problem. My mouse loses connection and is almost unusable. Rechargeable battery power meter shows power is full. This is new since the OS update and may be related to the dead Ethernet card. Not sure.

did you reboot the modem or just plug it in?

shut all devices down, modem and computer, reboot modem, let modem negotiate with your ISP and get connection, then connect to the Mac and turn the Mac on. Make sure you have a cable that works on other devices. It is not out of the question for the port to fail but it is more likely (in this type of situation) that the cable is "unfriendly" to the NIC card or the NIC card is "unfriendly" with that particular cable, try another cable. - This is know in cabalistic IT circles as "cable voodoo"

If that fails make sure you Mac is not set to a static IP in the config from the router, or if your ISP requires configuration outside DHCP you need to find out from them what that is.

Try different Ethernet cables to verify the if it's the port or a cable. Cables can and do fail on occasion. Once you have narrowed down if it's the cable or not you can do some basic resets such as resetting the SMC 2-3 times back to back and resetting the PRAM. If the problem continues then it may be hardware. Considering the Ethernet port (and all the other ports) are part of the main logic board this would mean you need to replace that board. On a 8 year old computer that does not make a lot of sense though.

iMac SMC and PRAM reset instructions.

I have the same problem with my iMac 27" (Late 2012). I first noticed this when I was still using El Capitan but was advised by Apple Support that upgrading to Sierra (11.12.6) might solve it. No, it didn't. I have checked the Ethernet cable from my ISP modem with my MacBook Pro and it--and the modem Ethernet port I was using--are fine. Most troubling is that under About This Mac>System Report>Ethernet Cards, I get the status report "This computer does not appear to have any PCI Ethernet cards installed." Prior to noticing this problem I was using the Ethernet port frequently. By coincidence (?), my iMac's Card Reader is also not recognized under System Report: "This computer doesn't contain any Apple Internal Memory Card Readers." I had been using the Card Reader often until it suddenly no longer worked. I have gone through the SMC & PRAM resets various times, but with no change in Ethernet (or Card Reader) status. Apple Support has suggested a "clean install" of Sierra and avoiding migration of system files, documents and settings, but I'm loathe to go through all that if a simpler solution is out there. Any further thoughts, anyone?