4.7 EXPLANATION OF ABBREVIATIONS AND TERMS 4.7 EXPLANATION OF ABBREVIATIONS AND TERMS The following abbreviations and terms listed in Table 4-1, will be used throughout the electrical flowcharts. Abbreviations Terms A/C Air  Conditioning ACG Air Compressor  Governor A/D Analog to Digital:  The computer inside the ECM uses an A/D converter to convert a sensor voltage into a number with which the computer can work. ASR Anti-Skid Regulation:  Data supplied by the ECM for use with ABS (anti-lock braking system). ATI Auxiliary Timed  Input ATS Air  Temperature Sensor:   Monitors engine air  temperature. BAT Battery BOI Beginning of Injection:  The number of crank angle degrees, before top-dead-center (TDC), where the ECM is requesting the injectors be turned on. BPS Bypass Position  Sensor CAN Controller Area Network:  J 1939 high speed control  data  link. CCM Crankcase Monitor Sensor:  Monitors crankcase pressure (currently on 149 engines only). CCPS Crankcase Pressure Sensor CEL * Check Engine Light:  Typically mounted on the instrument panel.  The CEL has two functions:1.  It is used as a warning lamp to inform the operator of the vehicle that a fault has occurred and the unit should be taken in for service as soon as possible.2.  It is used by the operator or technician to "flash out inactive trouble codes to help diagnose a problem. CKT Circuit CLS Coolant Level Sensor:  Monitors coolant level at the radiator top tank or heat exchanger. COM Common CPS Coolant Pressure Sensor:  Monitors coolant presssure. CTS Coolant  Temperature Sensor:   Monitors coolant  temperature. DDEC Detroit Diesel Electronic Controls DDEC  III Third generation Detroit Diesel Electronic Controls DDEC  IV Fourth generation Detroit Diesel Electronic Controls All information subject to change without notice. 4-12 6SE497  9709   Copyright © 1997 DETROIT DIESEL CORPORATION