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TM9-2320-360-20-3
Section 2
BASIC KNOWLEDGE REQUIRED (Cont’d)
D. EXPLANATION OF ABBREVIATIONS/TERMS
A/D
- 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.
BAT
- Battery
BOI
- Beginning of Injection: The number of crank angle degrees, Before Top Dead Center, where the ECM is
requesting the injectors be turned on.
CAN
Controller Area Network: J1939 High speed control data link.
CEL
- Check Engine Light: Typically mounted on the instrument panel. It has two functions:
1. 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.
2. 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.)
CGL
- Check Gauges Light: Typically mounted on the instrument panel. It has two functions:
1. It is used as a warning to the operator that a potential engine damaging condition has been detected.
2. It is used by the operator or technician to “flash” out active trouble codes.
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.
CKT
- Circuit
CLS
- Coolant Level Sensor: Monitors coolant level at the radiator top tank or heat exchanger.
CP
- Crankshaft Position: An ECM output generated anytime an SRS signal occurs.
COM
- Common
CTS
- Coolant Temperature Sensor: Monitors coolant temperature.
DDEC III - Third generation Detroit Diesel Electronic Controls.
DDL
- Diagnostic Data Link: The lines (wires) over which the ECM transmits information which can be read by a
Diagnostic Data Reader.
DDL+
- Data Link, Positive side: J1587 data link.
DDL-
- Data Link, Negative side: J1587 data link.
H-5
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