I have 3 problems with my Motherboard DZ77RE-75K.
1) the PCH Temperature sensor works sometimes and then stops working and reports a temp of 0 degrees as reported by the Intel Desktop Utilities
2) I installed 2x8 Gigs RAM modules by Corsair (Vengeance Pro 1866MHz) and the Motherboard will only run them at 1333MHz. At 1866MHz and using the default Bios settings, the PC will not boot
3) the Motherboard doesnt seem to control the speed of the PWM Rear Exhaust fan. The Fan's speed stays constant no matter how hot the case gets. The Fan is connected to the Rear Fan Header on the Motherboard
Pls help and thanks.
Did you try updating the BIOS? Do a BIOS recovery even if using the latest version.
http://www.intel.com/support/motherboards/desktop/sb/CS-023360.htm Desktop Boards — Instructions for Recovery BIOS Update
Try changing the rear fan with a different PWM capable fan.
In regards of the RAM, what is the exact part number or model? Are you using XMP (Extreme Memory Profile)?
If issue persists, test the motherboard with minimum components and power connections only, out of the case on a non-conductive surface.