TM 5-3805-290-23-1
THEORY OF OPERATION - CONTINUED
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ELECTRICAL SYSTEM - CONTINUED
10.
ECMs.
a.
Machine ECM. Machine ECM is an environmentally sealed unit. Machine ECM is mounted under cab on left side
of machine. Machine ECM is protected by a cover that must be removed in order to access machine ECM.
b.
Engine ECM. Engine ECM is a non-serviceable, environmentally sealed unit. Engine ECM is mounted on engine
on right side of machine. ECM functions as throttle and computer for fuel system. ECM receives all signals from
sensors in order to control timing and engine speed.
c.
Passwords in an ECM are used to:
(1)
Prevent reprogramming that is unauthorized
(2)
Prevent erasing of logged events that is unauthorized
d.
Factory passwords restrict changes to authorized personnel. Factory passwords are required to clear some event
codes.
e.
ECM has an excellent record of reliability. Any problems in system are most likely connectors and wiring harness.
ECM should be considered last in troubleshooting engine.
f.
Personality module contains software with all fuel setting information. Information determines engine perfor-
mance. Personality module is installed behind access panel on ECM.
g.
Flash programming is used in programming or updating personality module.
h.
ECM is sealed and needs no routine adjustment or maintenance.
11.
Speed/Timing Sensor. Primary engine position is a
passive sensor. Timing wheel is located on crankshaft.
Speed/timing sensor receives a signal from teeth on
timing wheel. Extra space on timing wheel gives one
revolution per space. Space is oriented so that space is
40 degrees after top center.
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