Isuzu N-Series. Service manual — part 940
Transmission Control System (Smoother) 7A-215
About Shift Clutch Control
Clutch solenoid valves are controlled so fluid pressure
operates the clutch assembly piston, which operates the
gearshift clutch to disengage and engage the clutch.
The clutch is disengaged while in neutral, and operates
before shifting and after shift control is complete.
When ATF temperature is low (up to 20
°C [68°F]), the
clutch engages in order to warm up the engine.
About Lockup Clutch Control
While running at or above a preset speed, the lockup
clutch engages in order to perform control that
eliminates engine power transmission loss.
• Lockup clutch engagement control
In 2nd and higher gears, the lockup clutch engages
when the following conditions are satisfied: shift
clutch is engaged, input shaft speed is 900 to 1500
rpm (vehicle speed depends on gear position), etc.
In the case of Rev or 1st gear, the lockup clutch
does not engage.
• Lockup clutch disengagement control
The lockup clutch disengages when the following
conditions are satisfied: input shaft speed is 900 to
1500 rpm (input shaft speed depends on gear
position), etc.
About Engine Speed Control
When the clutch is released (for shifting, etc.), a request
for engine speed change is sent to the engine control
module (ECM), and engine blowup and deterioration of
feeling (shift shock etc.) are prevented.
1st Gear Start Control
Turning on the 1st gear start switch causes the normal
start gear (2nd) to change to 1st gear. This can be used
when power is required due to payload and inclines.
Controlled
accelerator
Controlled accelerator
Actual accelerator
Actual accelerator
Required engine speed
Required engine speed
(at gearshift)
Input shaft speed
Input shaft speed
Actual engine speed
Actual engine speed
Low
High
Engaged
Disengaged
T
ransmission speed
Engine speed
Shift clutch control
Shift up control
Shift down control
Acceler
ator
opening angle
N7A2004E
7A-216 Transmission Control System (Smoother)
Running Mode Control
Shift control is change automatically in accordance with
the selected mode, and switches between fuel economy
mode and normal mode. There are two modes:
NORMAL mode and ECONO mode.
Starter Inhibitor Control
Starter inhibitor control makes it impossible to start the
engine when the selector lever is in any position other
than neutral.
PTO Control
PTO mode ON/OFF control is performed in accordance
with the PTO switch input gear position, parking brake
switch, and other inputs.
Determination of PTO control is possible
• Gear: Neutral
• Vehicle speed: Stopped
• PTO switch: ON
• Engine speed: Running (idling)
• Accelerator opening angle: OFF (idling)
• Parking brake: ON
Determination of PTO control is possible
• PTO switch: OFF
• Engine stopped
• Selector lever operation during PTO operation
• In neutral, vehicle speed is greater than 20 km/h
(12 MPH)
• Emergency switch: ON
Shift Control Limit
Automatic shifting prohibited while vehicle is running.
About The Starting Gear
The starting gear can be selected from among 1, 2 and
Rev, and shifting from the starting gear is not possible.
(The starting gear is fixed. However, shifting to neutral is
possible.)
Engine control
module (ECM)
Transmission control module
(TCM)
Starter relay
(NO)
ECM
main relay
Starter
Starter cut
relay (NO)
"Starter switch
""START"" position"
Emergency
relay (NO)
Emergency
switch
Gear control
solenoid relay (NO)
Emergency
shift switch
1-3-5
shift
solenoid
2-4-6-R
shift
solenoid
Select
solenoid
Selector lever
Neutral
switch
1st gear
start switch
Economy
mode
switch
Gear
shift
position
sensor
Gear
select
position
sensor
N7A2005E
Transmission Control System (Smoother) 7A-217
Emergency System Control
Turning on the emergency switch operates the
emergency relay and enables starter relay operation,
which makes it possible to operate the starter. The
emergency shift switch is also enabled, and switch
operation can be used to shift to R, neutral, and 1st.
Notice:
Shifting with the selector lever is not possible when the
emergency switch is turned on.
Engine control
module (ECM)
PTO
lamp
PTO
switch
PTO lever
switch
Transmission
control
module
(TCM)
Meter
N7A2095E
Legend
1. 1st Gear Start Switch
2. Selector Lever Unit
3. Selector Lever
4. Emergency Shift Switch
5. Emergency Switch
6. Economy Mode Switch
A
5
6
1
2
3
4
N7A2006E
7A-218 Transmission Control System (Smoother)
Inter-TCM Communication
The transmission control module (TCM) communicates
with the engine control module (ECM), EHCU (ABS/
ASR control unit), etc., and transfers engine speed,
vehicle speed, accelerator opening angle, ABS/ASR
operation, and other signals. CAN communication is
used for the communication system.
Half-Clutch Position Adjustment Function
The half-clutch point (gear engagement point) is
adjusted by pressing the FAST side or SLOW side of the
clutch adjustment switch. The procedure is: select the
neutral gear, pull the parking brake, and then press
“FAST” for fast clutch engagement or “SLOW” for slow
engagement. Adjustment is possible to four levels on
each side.
Important:
When ATF temperature is unstable, accurate learning is
not possible for half-clutch position adjustment.
Perform the adjustment operation after warming up the
engine sufficiently. If the half-clutch position does not
feel right after adjustment, repeat half-clutch adjustment
as required.
(In this case, it is not necessary to clear the current
learned value. Half-clutch adjustment can be performed
consecutively.)
It is easy to obtain a stable position at an ATF
temperature of 40
°C (104°F) or higher (directly after
running), which can be checked using scan tool (Tech
2).
Engine
Control
Module
(ECM)
Transmission
Control
Module
(TCM)
N7A2007E
N7A2008E
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