Circuit Description

When the ignition switch is turned ON, the main relay turns ON (the contact point closes) and the main power is supplied to ECM. And then ECM supplies 5 V power to each sensor (MAP sensor, A/C refrigerant pressure sensor, TP sensor and pressure sensor (included in EVAP leak check module).

If 5 V power circuit to each sensors from ECM is shorted to ground, ECM stops engine and emission control operation.