4.7 EXPLANATION OF ABBREVIATIONS AND TERMS Abbreviations Terms PTO Power Take-Off.   Also, referred  to  as VSG (Variable Speed Governor). PW Pulsewidth PWM Pulsewidth Modulated:  Modulated signal provided by  the DDEC  system. RES/ACCEL Resume/Accelerate Switch used for cruise control. SEL † Stop Engine Light: Typically mounted on the instrument panel. It has two functions:1.It is used as warning to the operator that a potential engine damaging condition has been detected.  If the DDEC system is programmed for shutdown, the engine will shutdown on its own within 30 seconds.  The engine should not be run until the condition is corrected.2.It is used by the operator or technician to "flash" out active trouble codes. SEO Stop Engine Override: Allows the stop engine condition to be overridden in case it is required. SET/COAST Set/Coast Switch:  Used in cruise control. SRS Synchronous Reference Sensor:  Indicates a specific cylinder in the firing order. TBS Turbocharger Boost Sensor:  Monitors turbo boost. TBD To  be  determined. TD Tachometer Driver:  An output from the ECM for electronic tachometers and or data loggers. TPS Throttle Position Sensor: Used to detect throttle request (a component of the EFPA). Also, referred to as LSG. TRS Timing Reference Sensor:  Used to detect whenever any cylinder is about to be fired. VIH Vehicle Interface Harness (OEM Wiring) VIN Vehicle Identification Number VSG Variable Speed Governor.   Also, referred to as PTO (Power  Take-Off). VSS Vehicle Speed Sensor:  Used to detect vehicle speed. VSS  OC Vehicle Speed Sensor Open Collector:  An ECM input which must be used in addition to the VSS positive input when certain types of vehicle speed sensors are used.   Refer to the Application and Installation manual for installation. * As a light bulb check and system check, the check engine light will come on for about 5 seconds when the ignition is turned on. If the CEL remains on, or comes back on, the self diagnostic system has detected a problem. If the problem goes away, the light will go out, but a trouble code will be stored in the ECM as an inactive code. † As a light bulb check and system check, the stop engine light will come on for about 5 seconds when the ignition is turned on. Table 4-1 Abbreviations and Terms All information subject to change without notice. 4-14 6SE497  9709   Copyright © 1997 DETROIT DIESEL CORPORATION