BASIC KNOWLEDGE REQUIRED (Cont'd.)
D. EXPLANATION OF ABBREVIATIONS/TERMS
Analog to Digital: The computer inside the ECM uses an A/D converter to convert a sensor
voltage into a number which the computer can work with.
Anti-Skid Regulation: Data supplied by the ECM for use with ABS (Anti-lock Braking System).
Air Temperature Sensor: Monitors engine air temperature.
Brake/Clutch Switch: Used in Cruise Control to determine whether the brake is depressed,
thus disabling cruise.
Beginning of Injection: The number of crank angle degrees, Before Top Dead Center, where
the ECM is requesting the Injectors be turned on.
Bypass Position Sensor
Cruise Active Light: Typically mounted on the instrument panel. Its main function is to turn on
when cruise control is operational. The CAL is no always used.
Controller Area Network: J1939 High speed control data link.
Crankcase Monitor Sensor: Monitors crankcase pressure (currently on 149 engines only).
-Check Engine Light: Typically mounted on the instrument panel. It has two functions:
It is used as a warning lamp to tell the operator of the vehicle that a fault has occurred and the unit should
be taken in for service as soon as possible.
It is used by the operator or technician to "flash" out inactive trouble codes to help diagnose a problem.
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. (See
general diagnostic information, section 2E for details.)
Coolant Level Sensor: Monitors coolant level at the radiator top tank or heat exchanger.
Crankshaft Position: An ECM output generated anytime an SRS signal occurs.
Coolant Pressure Sensor: Monitors coolant temperature.
Coolant Temperature Sensor: Monitors coolant temperature.
Third generation Detroit Diesel Electronic Controls.
Diagnostic Data Link: The lines (wires) over which the ECM transmits information which can
be read by a Diagnostic Data Reader.
Data Link, Positive side: J1587 data link.
Data Link, Negative side: J1587 data link.
Change 3 3-345.9