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Automatic Transmission – 4L60E – General Information Page 7C1–9
3 Transmission Control Module
Operation Overview
3.1 Transmission Control Module
W ith the introduction of the new HFV6 engine, the powertrain architecture has been redesigned to accommodate this
introduction. W ith this design, a new bus architecture and protocol has also been introduced. The new bus connects the
following modules:
• engine control module (ECM),
• transmission control module (TCM),
• powertrain interface module (PIM) and
• ABS module.
The protocol used to communicate between these modules is called General Motors Local Area Network (GM LAN)
which is based on Controller Area Network (CAN) communication protocol. For further information on GM LAN protocol
and data bus structure, refer to 6E1 Powertrain Interface Module – V6.
Component Location
The TCM (1) is located under the instrument panel, it is attached to a bracket mounted to the firewall as shown in
Figure 7C1 – 2.
For the other components using the GM LAN databus, refer to 6E1 Powertrain Interface Module – V6.
Figure 7C1 – 2
Transmission Control Module Data Transfer
The TCM uses various information to control the shift of the transmission. Besides the direct inputs from the various
transmission sensors directly into the TCM, the TCM uses data from the GM LAN databus.
The inputs/outputs directly connected to the TCM from the transmission are:
• shift solenoids,
• torque converter clutch control,
• pressure control solenoid,
• transmission fluid temperature sensor and
• vehicle speed sensor.
Refer to 3.2 TCM Wiring Diagrams.
The transmission also receives inputs from the park/neutral position and back up lamp switch assembly.
The TCM needs other various data parameters to control the transmission correctly. These include throttle plate angle,
whether cruise control is engaged and active or not, engine RPM etc. These are provided to the TCM from the ECM via
serial data using GM LAN communication protocol.
The TCM also supplies information that is used by other components and systems within the vehicle such as the engine
control module (ECM) and instrument cluster. Any information that is required on the body side of the data bus (UART
protocol) is translated by the powertrain interface module (PIM). For further information on the data bus structure, the
PIM and its operation, refer to 6E1 Powertrain Interface Module – V6.
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Automatic Transmission – 4L60E – General Information Page 7C1–10
Transmission Control Module Operation
The TCM processes data every 10 milliseconds from various sensors, such as throttle position, vehicle speed, gear
range, temperature, engine load and other inputs. The TCM compares all its various inputs with the internal programming
and calibration of the TCM using this data, a signal is transmitted to the valve body shift solenoids, which activate the
shift valves for precise shift control. Shift points are therefore precisely controlled and are identical from vehicle to vehic le.
The TCM also control torque converter clutch apply and release.
Shift feel is also electronically controlled by the TCM, by signals sent to the variable force solenoid, which controls fluid
line pressure and it is this pressure that precisely determines how the shifts will feel. In this way, the TCM electronically
synchronises the engine and transmission into a single integrated powertrain system for optimum performance, shift
timing, fuel efficiency and emission control.
3.2 TCM Wiring Diagrams
For details of the transmission control module (TCM) wiring diagrams, refer to 8A Electrical-Body and Chassis.
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Automatic Transmission – 4L60E – General Information Page 7C1–11
4 Transmission Definitions and
Abbreviations
The following definitions and abbreviations are provided to establish a common language and assist the user in
describing transmission related conditions. The use of these terms and/or conditions can be found in the various parts of
the automatic transmission sections, but more particularly in 7C3 Automatic Transmission – 4L60E – Hydraulic and
Mechanical Diagnosis.
4.1 Throttle Position Related Definitions
Throttle Position Definition
Minimum Throttle The least amount of throttle opening required for an upshift.
Light Throttle Approximately 1/4 of accelerator pedal travel (25% Throttle Position).
Medium Throttle Approximately 1/2 of accelerator pedal travel (50% Throttle Position).
Heavy Throttle Approximately 3/4 of accelerator pedal travel (75% Throttle Position).
Wide Open Throttle (WOT) Full travel of the accelerator pedal (100% Throttle Position).
Full Throttle Detent Downshift A quick apply of the accelerator pedal to its full travel, forcing a downshift.
Zero Throttle Coast Down A full release of the accelerator pedal while the car is in motion and in drive range.
Engine Braking A condition where the engine is used to slow the car by manually downshifting
during a zero throttle coast down.
4.2 Noise Condition Related Definitions
Noise Condition Definition
Planetary Gear Noise A whine related to car speed most noticeable in first gear or reverse. Becomes less
noticeable after an upshift.
Pump Noise A high pitch whine increasing with engine r.p.m.
4.3 General Definitions
General Definition
Accumulator A component of the transmission that absorbs hydraulic pressure during the apply of a
clutch or band. Accumulators are designed to control the quality of a shift from one gear range to another.
Adaptive Learning Programming within the TCM that automatically adjusts hydraulic pressures in order to compensate for changes in the transmission (i.e. component wear).
Applied An 'Applied Component' is holding another component to which it is splined or
assembled to. Also referred to as "engaged".
Apply Components Hydraulically operated clutches, servo’s, bands and mechanical one-way roller or
sprag clutches that drive or hold members of a planetary gear set.
Apply Plate A steel clutch plate in a clutch pack, located next to the (apply) piston.
Backing Plate A steel plate in a clutch pack that is usually the last plate in that clutch assembly
(furthest from the clutch piston).
Band An apply component that consists of a flexible strip of steel and friction material that
wraps around a drum. When applied, it tightens around the drum and prevents the drum from rotating.
Brake Switch An electrical device that provides signals to the transmission control module (TCM),
based on the position of the brake pedal. The TCM uses this information to apply or
release the torque converter clutch (TCC).
Centrifugal Force A force that is imparted on an object (due to rotation) that increases as that object moves further away from a centre-point of rotation.
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Automatic Transmission – 4L60E – General Information Page 7C1–12
General Definition
Check Ball A spherical, hydraulically controlled component (usually of steel) that either seals or
opens fluid circuits. It is also referred to as a check valve.
Clutch Pack An assembly of components generally consisting of clutch plates, an apply plate and a
backing plate.
Clutch Plate A hydraulically activated component that has two basic designs: (1) all steel, or (2) a
steel core with friction material bonded to one or two sides of the plate.
Control Valve Body A machined metal casting that contains valve trains and other hydraulically controlled components that shift the transmission.
Coupling Speed The speed at which a vehicle is travelling and no longer requires torque multiplication through the torque converter. At this point, the stator 'free wheels' to allow fluid leaving
the turbine to flow directly to the pump. (Also see Torque Converter).
De-energise(d) To interrupt the electrical current that flows to an electronically controlled device,
making it electrically inoperable.
Direct Drive A condition in a gears set where the input speed and input torque equals the output
speed and output torque. The gear ratio through the gear set is 1:1.
Downshift A change in a gear ratio where both input speed and torque increases.
Duty Cycle In reference to an electronically controlled solenoid, it is the amount of time (expressed
as a percentage) that current flows through the solenoid coil.
Energise(d) To supply a current to an electronically controlled device, enabling it to perform its
designed function.
Engine Compression Braking A condition where compression from the engine is used with the transmission to decrease vehicle speed.
Exhaust The release of fluid pressure from a hydraulic circuit. (The words 'exhausts' and
'exhausting' are also used and have the same intended meaning.)
Fail-safe Mode A condition whereby a component (i.e. engine or transmission) will partially function even if its electrical circuit is disabled.
Fluid In this Section of the Service Manual, 'fluid' refers primarily to automatic transmission
fluid (or ATF) and, for the Hydra-matic 4L60E transmission, the only recommended
fluid is Dexron
III.
Fluid Pressure A pressure that is consistent throughout a given fluid circuit.
Force A measurable effort that is exerted on an object (component).
Freewheeling A condition where power is lost through a driving or holding device (i.e. roller or sprag
clutches).
Friction Material A heat and wear resistant fibrous material, bonded to clutch plates and bands.
Gear A round, toothed device that is used for transmitting torque through other components.
Gear Range A specific speed to torque ratio at which the transmission is operating (i.e. 1st gear,
2nd gear etc.).
Gear Ratio Revolutions of an input gear as compared to the revolutions of an output gear. It can
also be expressed as the number of teeth on a gear as compared to the number of
teeth on a gear that it is in mesh with.
Hydraulic Circuit A fluid passage which often includes the mechanical components in that circuit
designed to perform a specific function.
Input A starting point for torque, revolutions or energy into another component of the
transmission.
Internal Gear The outermost member of a gear set that has gear teeth in constant mesh with the
planetary pinion gears of the gear set.
Land (Valve Land) The larger diameters of a spool valve that contact the valve bore or bushing.
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Automatic Transmission – 4L60E – General Information Page 7C1–13
General Definition
Line Pressure The main fluid pressure in a hydraulic system created by the pump and pressure
regulator valve.
Manual Valve A spool valve that distributes fluid to various hydraulic circuits and is mechanically
linked to the gear selector lever.
Orifice A restricting device (usually a hole in the spacer plate) for controlling pressure build up
into another circuit.
Overdrive An operating condition in the gear set allowing output speed to be higher than input
speed and output torque to be lower than input torque.
Overrunning The function of a one-way mechanical clutch that allows the clutch to freewheel during certain operating conditions of the transmission.
Pedal Position The percentage angle of the accelerator pedal as displayed by Tech 2.
Pinion Gears Pinion gears (housed in a carrier) that are in constant mesh with a circumferential
internal gear and centralised sun gear.
Planetary Gear Set An assembly of gears that consists of an internal gear, planet pinion gears with a carrier, and a sun gear.
Pressure A measurable force that is exerted on an area and expressed as kilopascals (kPa).
Pulse Width Modulated (PW M) An electronic signal that continuously cycles the On and Off time of a device (such as
a solenoid) while varying the amount of On time.
Race (Inner or Outer) A highly polished steel surface that contacts bearings or sprag or roller elements.
Reduction (Gear Reduction) An operating condition in the gear set allowing output speed to be lower than input speed and output torque to be higher than input torque.
Residual Fluid Pressure Excess pressure contained within an area after the supply pressure has been terminated.
Roller Clutch A mechanical clutch (holding device) consisting of roller bearings assembled between inner and outer races.
Servo A spring loaded device consisting of a piston in a bore that is operated (stroked) by
hydraulic pressure to apply or release a band.
Spool Valve A round hydraulic control valve often containing a variety of land and valley diameters.
Sprag Clutch A mechanical clutch (holding device consisting of "figure eight" like elements
assembled between inner and outer races.
Staking The effect of deforming, peening over or riveting a shaft to provide a solid mounting.
Throttle Position The travel of the throttle plate that is expressed in percentages and measured by
Tech 2.
Torque A measurable twisting force expressed in terms of Newton metres (Nm).
Torque Converter A component of an automatic transmission, (attached to the engine flex plate) that
transfers torque from the engine to the transmission through a fluid coupling.
Torx Plus Bit A special tool used for the removal of the bell housing. Precision tip fit means that cam
out of the bolt head is virtually eliminated.
NOTE
Torx
Plus Bits are different from normal Torx
Bits
Transmission Control Module
(TCM) An electronic device that manages the vehicle's engine and automatic transmission
functions.
Variable Capacity Pump The device that provides fluid for operating the hydraulic circuits in the transmission. The amount of fluid supplied varies depending on vehicle operating conditions.
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Automatic Transmission – 4L60E – General Information Page 7C1–14
4.4 Abbreviations
Abbreviation Definition
2W D Two W heel Drive.
AC Alternating Current
A/C Air Conditioning
AFL Actuator Feed Limit
4W D Four W heel Drive
DC Direct Current
D.C Duty Cycle
DLC Diagnostic Link Connector
DTC Diagnostic Trouble Code
ECM Engine Control Module
ECT Sensor Engine Coolant Temperature Sensor.
ETC Electronic Throttle Control
N.C Normally Closed
N.O. Normally Open
PCS Pressure Control Solenoid (or Force Motor)
PIM Powertrain Interface Module
PW M Pulse W idth Modulated
RWD Rear Wheel Drive.
TCC Torque Converter Clutch.
TCM Transmission Control Module
TFP Switch Transmission Fluid Pressure Manual Valve Position Switch
TFT Transmission Fluid Temperature Sensor.
TP Sensor Throttle Position Sensor.
VS Sensor Vehicle Speed Sensor.
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Automatic Transmission – 4L60E – General Information Page 7C1–15
5 Service Notes
In the interests of safety to personnel, equipment and to the vehicle and its components, read and adhere to the following
notes whenever servicing operations are to be carried out on the Hydra-matic 4L60E automatic transmission. In addition,
some of this information also refers to sound workshop practices and, to achieve the design life of affected components.
Fasteners
• Always reinstall fasteners in the same locations as they were removed.
• If a fastener requires replacement, always use a part of the correct part number or of equal size and strength or
stronger.
General Workshop Practice
• Keep work area and tools clean.
• To avoid unnecessary contamination, always clean the exterior of the transmission before removing any parts.
• Do not use wiping cloths or rags because of the risk of lint being trapped in the transmission.
• Do not use solvents on:
• neoprene seals,
• composition faced clutch plates, or
• thrust washers.
• Always wear eye protection when using compressed air.
• Blow out all passages with compressed air. Only probe small passages with soft, thin wire.
• Handle parts with care to avoid nicks and scratches.
• Do not remove Teflon oil seal rings unless damaged or performing a complete overhaul.
• Expand internal snap rings and compress external snap rings to maximise retention and security.
• Lubricate all internal parts with transmission fluid (only use Dexron® III), as they are being installed.
• When installing cap screws into aluminium castings:
• always use a torque wrench and
• stripped or damaged threads in aluminium castings may be reconditioned by using commercially available
thread inserts.
• Once removed, replace all gaskets, seals and O-rings with new parts.
• Always use seal protectors where indicated and do not use gasket cement or sealant on any joined face unless
specified to do so.
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Automatic Transmission – 4L60E – General Information Page 7C1–16
6 Torque Specifications
Oil pan attaching bolt ............................................................................ 12.0 Nm
Shift selector base plate attaching nut ................................................... 7.0 Nm
Spring plate attaching screw .................................................................. 2.0 Nm
Selector lever knob attaching screw ....................................................... 2.0 Nm
Selector cable bracket attaching bolt.................................................... 22.0 Nm
Heat shield front attaching screw .............................................. 15.0 – 35.0 Nm
Heat shield rear attaching screw ............................................................ 9.0 Nm
Manual shaft linkage attaching nut ...................................................... 25.0 Nm
Neutral start and back-up lamp switch attaching screw............. 15.0 – 35.0 Nm
Vehicle speed sensor attaching bolt ........................................... 11.0 - 14.0 Nm
Transmission mount attaching bolt ...................................................... 50.0 Nm
Transmission support attaching bolt and nut ............................. 50.0 – 65.0 Nm
Transmission mount attaching nut ....................................................... 52.0 Nm
Heat shield to transmission support attaching bolt ............................... 52.0 Nm
Extension housing attaching bolt ............................................... 42.0 – 48.0 Nm
1 – 2 Accumulator cover attaching bolt................................................. 12.0 Nm
TCC solenoid attaching bolt ................................................................. 12.0 Nm
Control valve body attaching bolt ......................................................... 12.0 Nm
Transmission fluid pressure (TFP) manual valve
position switch attaching bolt ................................................................ 12.0 Nm
Manual detent spring attaching bolt ...................................................... 23.0 Nm
Spacer plate support plate attaching bolt ............................................. 12.0 Nm
Filler tube bracket attaching bolt................................................ 20.0 – 35.0 Nm
Vent pipe attaching bolt .......................................................................... 6.0 Nm
Transmission cooler lines bracket attaching screw .............................. 23.0 Nm
Torque converter housing attaching bolt ................................... 52.0 – 66.0 Nm
Torque converter to flexplate attaching bolt............................... 60.0 – 70.0 Nm
Torque converter cover attaching bolt ....................................... 12.0 – 16.0 Nm
TCM bracket attaching nut ..................................................................... 7.0 Nm
TCM attaching bolt and nut .................................................................... 7.0 Nm
Oil Pump Cover to Pump Body Attaching Bolt...................................... 25.0 Nm
Pressure Control Solenoid Retainer Attaching Bolt .............................. 12.0 Nm
Forward Accumulator Cover Attaching Bolt .......................................... 12.0 Nm
Oil Pump to Transmission Case Attaching Bolt .................................... 30.0 Nm
Torque Converter Housing to
Transmission Case Attaching Bolt............................................. 65.0 – 75.0 Nm
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