SELF-DIAGNOSTIC APPARATUS IN MEASURING APPARATUS OF FLOW RATE OF SUCTION AIR OF INTERNAL COMBUSTION ENGINE

摘要

PURPOSE:To detect the detecting characteristic per every level of the flow rate of the suction air and to enable self-diagnosis of the abnormality of an apparatus by connecting a plurality of diagnosing resistances selectively to a bridge circuit. CONSTITUTION:A diagnostic resistance separately provided from a resistance to form a bridge circuit in a diagnostic resistance connecting means is selectively connected to the bridge circuit, so that the balance of the resistance in the bridge circuit when the general amount of the suction air is measured is forcibly changed thereby to produce the state where the amount of the suction air appears to be changed. A detecting value sampling means connects a plurality of the diagnosing resistances selectively to the bridge circuit by the diagnostic resistance connecting means when the engine is stopped, that is, when the flow rate is zero. Detecting signals of the flow rate of the suction air per every resistance value are sampled. A plurality of the sampled detecting signals are compared with an expecting value corresponding to the resistance value changed by the diagnostic resistance, whereby the abnormality of the measuring apparatus of the flow rate of the suction air can be detected by an abnormality detecting means.