Isuzu N-Series. Manual - part 939

Transmission Control System (Smoother) 7A-211

Gear Position Indicator

The gear position indicator indicates the transmission
gear position as detected by the TCM. The gear position
indicator is installed within the instrument panel cluster
(IPC). 

Transmission Warning Lamp 

The transmission warning lamp lights or blinks when the
following conditions occur. 

• If trouble is detected by the system during normal

running, the lamp lights or blinks. 

• The warning lamp blinks when the emergency

switch is on. 

• If the Smoother system transmission fluid

temperature rises to an abnormal level during
normal running, the lamp blinks. 

• The lamp blinks during learning. 

Legend

1. Gearshift Control Box 
2. 1-3-5 Shift Solenoid Valve
3. 2-4-6-R Shift Solenoid Valve
4. Gear Select Positin Sensor
5. Gear Shift Position Sensor
6. Neutral Switch

Legend

1. Gear Position Indicator

N7A2018E

N7A2010E

Legend

1. 1st Gear Start Indicator Lamp
2. Economy Mode Indicator Lamp
3. Transmission Warning Lamp 

N7A2011E

7A-212 Transmission Control System (Smoother)

Turbine Speed Sensor 

The turbine speed sensor is a pickup type sensor
installed in the transmission, which generates a signal
when it is passed by the turbine pulser. The turbine
speed sensor signal is used for gear shift control (lockup
control, clutch control, etc.) based on signals input from
the input shaft speed sensor, vehicle speed sensor, etc. 

Vehicle Speed Sensor

The vehicle speed sensor is installed in the
transmission. The vehicle speed sensor signal is
obtained from the ECM using CAN communication. 

Smoother System Description

Smoother System Overview

“Smoother” is the name of a new-generation drive train
that provides benefits in terms of both life cycle costs
(low initial cost and maintenance cost, lower fuel
consumption, etc.) and easy driving. Smoother is a
system that adds an automatic transmission to the
existing Smoother, for even better fuel consumption and
easier driving. This is accomplished by installing a
solenoid system gearshift control box on the Smoother,
which combines a manual transmission with fluid
coupling, so all shifting is performed automatically in
accordance with signals from the transmission control
module (TCM). When starting moving the vehicle,
depressing the brake pedal and operating the change
lever as on an automatic vehicle causes a selector lever
position signal to be detected by the TCM. This actuates
the gearshift control box solenoid and shifts the gear into
the starting position or the reverse position, and then
engages the shift change clutch (gearshift). (After the
shift clutch engages, creep force is generated the same
as on an AT vehicle.) Releasing the foot from the brake
pedal and pressing the accelerator pedal starts the
vehicle moving forward. If there is an up-shift or down-
shift while running, the control unit determines the
vehicle status based on vehicle speed, accelerator
opening angle, and other factors, and shifts to the
optimal gear automatically. If the driver movers the
change lever in the “+” or “

−” direction, a gear change is

indicated, so sequential manual shifting is also possible.
(Even during sequential manual shifting, the
transmission shifts to the starting position when the
vehicle is stopped.) 

N7A2023E

N7A2031E

Transmission Control System (Smoother) 7A-213

About Control

The transmission control module (TCM) has the
following functions, which perform various types of
control. 

1. Transmission shift control 

Shift control is performed automatically as required
by vehicle conditions, shift mode, 1st gear start,
etc. Shift control is performed by controlling the
change lever, shift control box assembly, etc.
(Manual operation is also supported, and the
driver's intentions are giving top priority.) 

• Shift up, shift down control 

• Shift clutch control
• Lockup clutch control 
• Engine speed control
• 1st gear start control 

2. 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. 

Legend

1. Selector Lever

6. Engine Control Module (ECM)

2. Transmission Control Module (TCM)

7. Accelerator Opening Angle Signal

3. Gearshift Control Box Assembly

8. Brake Signal

4. Transmission Main Unit

9. Instrument Panel Cluster (Lamps, Indicators)

5. Engine

R

N

D

A

9

2

4

3

5

6

1

7

8

N7A2002E

7A-214 Transmission Control System (Smoother)

3. Starter inhibitor control

Neutral control and other control are performed
when the engine is being started. 

4. PTO control

Shift control is performed for PTO gear operation. 

5. Emergency system control 

Control is performed to enable engine start and
vehicle movement when system trouble is
detected. 

6. Inter-TCM communication 

Communication is performed with the engine
control module (ECM) and other devices, and
information transfer required for control is also
performed.

7. Self-diagnosis function

DTC are used to perform various tests to identify
the location of trouble and communication is

performed with scan tool, the DTC are confirmed,
etc. 

8. Information functions (indicator, lamp, buzzer

control) 
Gear position indicators show the current gear
position of the transmission, information lamps
indicate operation of each function, and a buzzer
alerts the driver to function operations, etc. 

9. Half-clutch adjustment function 

The half-clutch position can be adjusted by
operating a clutch adjustment switch. 

Transmission Shift Control 

Based on control signals from the selector lever unit,
gearshift control box solenoids (shift, select) are
controlled in accordance with engine speed,
transmission turbine speed, input shaft speed, vehicle
speed, accelerator opening angle, and other factors to
perform the shift operation. 

About Shift Up, Shift Down Control 

Shift up/shift down is performed when the selector lever
position (mode) is “D”, and an automatic shift or selector
lever operation is performed in the “+” direction or “

−”

direction. Basically, shift clutch control and shift control

are performed based on engine speed, input shaft
speed, accelerator opening angle, etc. 

Legend

1. Select Solenoid Valve

4. Gear Shift Position Sensor

2. 1-3-5 Shift Solenoid Valve

5. Gear Select Position Sensor

3. 2-4-6-R Shift Solenoid Valve

 

 

 

 

N7A2003E