TM 5-3805-291-23-1
THEORY OF OPERATION - CONTINUED
0003 00
ENGINE - CONTINUED
b.
Electronic Controls.
(1)
ECM has three main functions: providing power for engine electronics, monitoring input signals from
engine sensors, and acting as a throttle to control engine rpm. ECM stores active faults, logged faults, and
logged events. Personality module is ECM software which contains specific maps to define power, torque,
and engine rpm.
(2)
ECM sends electrical current to output components to control engine operation. ECM has two 70-pin har-
ness connectors, engine harness connector, and machine harness connector. Machine harness connects
ECM to engine control portion of machine harness. Engine control portion includes these components:
Transmission
Brake
Clutch switches
Data links
CHECK ENGINE light
WARNING light
Engine retarded switch
Speedometer
Cooling fan solenoid
(3)
These features are also electronic control system responsibilities:
Cold start strategy
Oil pressure
Coolant temperature warning indicator
Automatic altitude compensation
Variable injection timing
Electronic engine speed governing
(4)
These features result in precise engine speed control, very little smoke, faster cold starting, and built-in
engine protection. There are two main ECM components: ECM itself and personality module. ECM is a
computer and personality module is computer software. Personality module contains operating maps
which define engine characteristics such as horsepower, torque curves, and rpm.
(5)
ECM determines desired engine rpm based on these criteria: throttle signal, certain diagnostic codes, and
machine speed signal. ECM maintains desired engine rpm by sensing actual engine rpm and calculating
amount of fuel injection necessary to achieve desired rpm.
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