Chosen Solution
iMac 21.5" Mid 2011 2.5 GHz Intel Core i5 Hello, I’m having trouble with my 21.5" iMac. After working for 2 - 3 hours the mouse with Bluetooth and USB port connected keyboard stop working. Sometimes I can work a whole day without any problems, other times it stops and I have to restart my system to get it working again. How can fix this? Thanks Update (02/26/2017)
I have this error: 4SNS/1/40000000: TH00-9.000
Someone put in a replacement HD and forgot to add in the needed hardware sensor if they put in a non-Apple drive the system came with. Here is the needed sensor: OWC In-line Digital Thermal Sensor for iMac 2011 Hard Drive Upgrade and here is the needed steps to get to it: iMac Intel 21.5" EMC 2428 Hard Drive Replacement. You can stop as Step12 to slide on the sensor for the drive you have now.
