Patent ID: 8548641

Claim:
A load drive circuit built into an electronic control device, which includes a control circuit that controls the load drive circuit with a load drive signal and which drives a load including at least one of a solenoid, relay, switch, heater, and a motor using a DC power supply as a power supply, the load drive circuit comprising: a switching element which turns ON and OFF in response to the load drive signal; and a diagnostic circuit which detects an abnormal state of the switching element, wherein a drive-stop signal output from the control circuit to the load drive circuit maintains an OFF state of the switching element without being affected by changes in the load drive signal from the control circuit, wherein, upon input of the drive-stop signal to the load drive circuit, the diagnostic circuit carries out a diagnosis on the load drive circuit in response to the load drive signal for detecting the abnormal state of the switching element to confirm a normal operational state of the diagnostic circuit, while being mounted in the electronic control device, wherein whether the diagnostic circuit is normally operating or not is checked during a system stop process that is executed during the period from the input of a power-off signal to the electronic control device until the power of the electronic control device is switched off, and wherein the load drive circuit is built into a vehicle's load drive device, and whether the diagnostic circuit is normally operating or not is checked during the system stop process, the system stop process being executed after an ignition key of a vehicle has been turned to an “off” position.