Circuit Description
The ECM continuously monitors it's internal memory status, internal circuits, and output signals to the throttle actuator. This self-check determines whether the ECM is functioning properly. If any malfunction is detected, the ECM will set the appropriate DTC and illuminate the MIL.
The ECM memory status is diagnosed by internal "mirroring" of the main CPU and the sub CPU to detect random access memory (RAM) errors. The two CPUs also perform continuous mutual monitoring. If there is a difference between outputs from the two CPUs that deviates from standard level ranges, the ECM concludes that there is a fault and sets a DTC. Additionally, if the signals to the throttle actuator deviate from the standard range or if the ECM detects malfunction in the throttle actuator supply voltage, the ECM will conclude that there is a fault and set a DTC. With any malfunction of the ECM, the MIL will be turned on and DTC (s) will be set.