Cummins ISB CM550 (1990-94) Fault Code: 489 PID: 191 SPN: 191 FMI: 0 Auxiliary Speed or Auxiliary Pressure Input Error

Circuit Description
The auxiliary speed input is a frequency signal from an auxiliary speed or pressure pickup. It is
sent to the electronic control module (ECM) and is used to control the engine speed. Auxiliary
reference speed is based on the throttle position.

Component Location
The auxiliary speed or pressure pickup device location is dependent on the original equipment
manufacturer’s (OEM) application. Refer to OEM manual for component location.

Shop Talk
The auxiliary speed governor controls engine speed based on a measured auxiliary speed or
pressure. The auxiliary speed governor feature must be enabled in the calibration and set
properly for speed or pressure, depending on the OEM application.

Categories Cumminz, DTC TRUCKS, ISB CM550 (1990-94) Tags 1990, 94, CM550, Cummins, FaultCode489, FMI0, ISB, PID191, SPN191

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