Diagnostic circuit for idling control switch of IC engine - has two-position switch and additional resistors for proving correct switch function or identifying fault

摘要

A circuit for checking the correct functioning of an idling control switch in an IC engine employs a two-position switch (16) with its common pole connected to an analogue/digital converter (12) which forms part of the engine control unit (10). The two positions of the switch (16) determine different voltage inputs to the A/D converter (12) at the terminal (18) corresp. to the resistor ratios R1/R2 or T1/R3 in order that idling or low idling conditions are signalled to the controller (10). Simple voltage checks to earth at the terminal (18) prove correct operation or not. USE/ADVANTAGE - Easy fault identification. Alterations require only two additional resistors and two position switch with no charges to remaining components.