Circuit description: Notes

The fuel pump circuit consists of the engine control computer, the fuel pump, and the fuel pump control computer ASSY (that operates the fuel pump). The engine control computer determines the operation speed of the fuel pump based on the engine output. The operation speed is converted to a load signal and sent to the fuel pump control computer ASSY. Then, based on the signal sent from the engine control computer, the fuel pump control computer ASSY adjusts the operation speed of the fuel pump from 3 speeds. The fuel pump control computer ASSY also has a self-diagnosis function. Based on the status of the fuel pump circuit, the fuel pump control computer ASSY outputs a diagnosis signal (DI) to the engine control computer. Then, the engine control computer determines if there is some trouble in the fuel pump circuit.