Idle Switch (Cadillac Except Brougham)

The ISC motor is equipped with an internal idle switch (also called a throttle or nose switch) which informs the ECM when it should be controlling idle.

Disconnect ISC connector. Connect an ohmmeter across Pink and Black/White wire terminals ("A" and "B") of ISC motor connector. See Fig 1 . With throttle closed, continuity should exist. With throttle open enough to relieve tension from the ISC plunger, continuity should not exist.

Fig 1: Idle Speed Control Solenoid/Idle Switch Schematic

Courtesy of GENERAL MOTORS CORP.