DTC Description: Notes
WARNING: This page is about a different car, the 2018 Nissan Titan XD. However, it is still accessible from the selected car via links, so may be relevant.
The Engine Control Module (ECM) is the brains for engine operation. It interprets signals from sensors to determine actuator positions and fueling control. The ECM gather and maintain data in its internal memory. The ECM receives constant voltage from the batteries through unswitched battery connections. It also receives switched battery input through the vehicle key switch wire when the vehicle is turned ON.
The ECM has internal diagnostics that continuously run and check the internal memory.