Drawing courtesy VW / Audi Group Drawing courtesy VW / Audi Group Figure 8: With higher coolant temperatures the electric stat can open like a conventional stat, but with heavier throttle events, the stat gets commanded open with a variable PWM signal to the electric heating element inside the thermostat. This can give a variable thermostat opening to tailor the engine temperature to the load. The higher the load, the lower we want the temperature in order to benefit from a denser air charge in the combustion event. Figure 9: The resistor heating element in these electric mapped thermostats works much like an O2 heater grid in a heated O2S. PWM signal from the ECM / PCM along with the associated DTCs when an electrical open or shorted condition occurs. The heater heats the wax (a job the coolant solely did traditionally) in order to move the lifting pin to overcome the stat's spring and move the large (and small) valve discs. August 2016 5 Chevy Cruze's electric thermostat heater you can clearly see (Fig 11) that the power to the heater grid is provided by a 10 amp fuse inside the underhood fuse block. In the case of this vehicle that same 10 amp fuse powers the engine's IMTV (Intake Manifold Tuning Solenoid Valve) so if the fuse is blown or there is a broken wire between the fuse block and harness splice there would not be power to either component. You will also notice (Fig. 11) that the ground is provided by the ECM. Basic theory of operation for any electrically mapped thermostat states that the computer doesn't do ANYTHING until either a heavy engine load is experienced or there is a MACS Service Reports