Motor Electronics Cooling Pump (MECP)
WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The motor electronics cooling system is required to maintain an acceptable temperature for the transaxle and the DC/DC converter. The system temperature is monitored by the motor electronics coolant temperature (MECT) sensor, which is an input to the PCM. The PCM commands the MECP using the MECP relay. The MECP is commanded on whenever the traction battery contactors are closed. The coolant in the system flows in a loop from the MECP, to the DC/DC converter, to the top hose port of the motor electronics radiator, out of the motor electronics radiator bottom hose port, into the transaxle, and back into the MECP. The cooling system has a degassing system built into the loop that bleeds air/gases into the coolant reservoir.