Code 21, Throttle Switch Circuit (M/T Only) Idle Switch & Wot Switch Indicated On

On manual transaxle vehicles, ECM supplies 4-5 volts to throttle switch on throttle body. When throttle is closed, ECM senses a low signal voltage on Lt. Green/Yellow wire. When throttle is opened slightly, ECM senses high signal voltage on Lt. Green/Yellow wire. When throttle is wide open, ECM senses low signal voltage on Lt. Green/White wire. Code 21 will be set if ECM senses signal voltage greater than 4-9 volts, for .3 second or more, at both ECM terminals A3 (Lt. Green/Yellow) and A15 (Lt. Green/White) at the same time.

1. A poor connection or a ground circuit will indicate a low signal.
2. Checks circuit for a short to ground or misadjusted throttle switch.
3. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section.