The CPU tries to save power and lowers itself into another power state but the power rail becomes unstable and the power to the CPU is shut down resulting in the machine turning off. The issues with the Mosfets present themselves mainly when you are doing very basic tasks and the MacBook is under minimum load such as web browsing. Every time a Mosfet is turned on its gate is stressed wearing away oxide and a process called gate oxide breakdown occurs. Over time the thickness of the 'gate' is reduced preventing the Mosfet from working as efficiently as it should be. Die attach degregation also occurs which changes the internal resistance of the mosfet.
Over many cycles and years bond wires crack and lift off occurs inside the Mosfet. Not exactly a graphics fault but the symptoms can be very similar to the Mid 2012 - Early 2013 issue so we will keep it in this section.Īfter years of use and thermal fatigue the Mosfets which accurately supply the correct voltage to the processor start to deteriorate. If your suffering unreliability issues with your Late 2013 to 2015 MacBook Pro 15 Inch A1398 the chances are it is suffering with a common problem with its CPU Mosfets. Late 2013 to 2015 15 Inch MacBook Pro A1398 Mosfet Repair