TM 5-3805-291-23-1
THEORY OF OPERATION - CONTINUED
0003 00
POWERTRAIN - CONTINUED
(5)
Pressure Switch (Secondary Steering).
(a) Secondary steering pressure switch is an input of powertrain ECM which informs powertrain ECM of
secondary steering system status.
(b) Secondary steering pressure switch is a double-pole, single-throw pressure switch. When secondary
steering pressure switch indicates pressure in secondary steering system, switch will change. Power-
train ECM will activate secondary steering warning indicator and set EMS warning level to Category
3. When secondary steering system functions correctly, N/O pole is closed and N/C pole is open.
N OT E
The normally closed (N/C) circuit and normally open (N/O) circuit of the secondary steering pressure
switch are used for diagnostic purposes. A circuit failure is present if the two circuits are open at the same
time or if the two circuits are grounded at the same time. This fault is then shown on the powertrain ECM
display.
(c) N/C pole connects to powertrain ECM connector contact J2-61. N/O pole connects to powertrain
ECM connector contact J2-60. Switch common terminal connects to ground.
(6)
Engine Start Switch.
(a) Engine start switch is an input of powertrain ECM which informs powertrain ECM of an attempt to
start engine. Powertrain ECM then initiates neutral start function.
N OT E
When the engine start switch is initially turned tothe START position, the switch will not return to the
START position from the ON position. The switch must be turned to the OFF position first before it
can be turned to the START position.
When the engine start switch is in the ON position,a +battery signal is sent to connector contact J1-1.
This activates the powertrain ECM.
(b) During normal machine operation, start terminal of engine start switch is open. When engine start
switch is turned to START position, start terminal closes to +battery and +battery voltage is present at
powertrain ECM connector contact J2-1. When all starting conditions are satisfied, powertrain ECM
sends a +battery signal to start relay connect contact J2-7 and engine cranking begins.
(7)
Switch (Transmission Direction and Shift Lever). Switches in transmission direction and shift lever are
powertrain ECM inputs which send information to powertrain ECM about selected speed and direction.
Switches close direction/speed inputs to ground on powertrain ECM.
(8)
Switch (Transmission Downshift). Downshift switch signals powertrain ECM to downshift transmission
by one speed. To downshift, operator depresses downshift switch. Switch has one input connection to pow-
ertrain ECM on connector J1: downshift N/O at contact 63. When operator presses downshift switch,
downshift N/O circuit is closed to ground. When downshift switch is not activated, downshift N/O circuit
is open or floating.
(9)
Rotary Switch (Autoshift Control). Autoshift switch tells powertrain ECM desired shift mode, AUTO or
MANUAL. Switch has three input connections to powertrain ECM on connector J1. Two switch contacts
are used for diagnosing a switch failure. A circuit failure is present if all three switch contacts are open
simultaneously, or if any two switch contacts are grounded simultaneously.
0003 00-37
