Chosen Solution
Hi, The CPU fan on my 2011 27” iMac is running at full speed. I ran the diagnostics and it gave the error code 4SNS/1/C0000008: TS2p—124 which seems to be the Right Skin Temperature sensor. I fitted a new sensor but the error code is still there. I’ve also checked the socket for the sensor on the motherboard and it’s making contact and isn’t loose. The problem started when I added an SSD drive so I may have dislodged something in the process. The ODD and HDD fans are operating normally. Is there anything else I could check or is there a way of disabling this sensor permanently?
Update (01/28/2021) Here’s an image of the board
The problem was a broken pin on the left skin sensor connection (not a problem with the right skin sensor as I originally thought). @danj thanks for you help with this one.
A common issue is in the process of disconnecting the sensor you damage the two small inductors L5500 & L5501. Here’s an image of the area:
