Automatic Transaxle - 4t45-e - Description and Operation Chevrolet Malibu VII

How to Use This Section

This section provides the following information

1. General diagnosis information on transmissions
2. Procedures for diagnosing the Hydra-matic transmission

When you diagnose any condition of the Hydra-matic transmission, begin with a Diagnostic Starting Point. This procedure indicates the proper path of diagnosing the transmission by describing the basic checks. This procedure will then refer you to the locations of specific checks. After you have determined the cause of a condition, refer to Repair Instructions for repair procedures.

Basic Knowledge

You must be familiar with some basic electronics in order to use this section of the service manual. You should also be able to use the following special tools

1. A digital multimeter (DMM)
2. A circuit tester
3. Jumper wires or leads
4. A line pressure gauge set

Scheme 161

All automatic transmissions have a metal identification (ID) nameplate (1) attached to the case exterior.

Scheme 162

The Hydra-Matic 4T45-E transmission has a metal identification nameplate (1) attached to the case exterior.

The information on the nameplate assists the technician in servicing the transmission and ordering replacement parts from a GM Parts Catalog.

Additional transmission identification information is provided on the Service Parts Identification label. This label shows the Regular Production Options (RPO) as well as the standard and mandatory options. This label is affixed to the inside of each vehicle at the assembly plant.

TAP Shift Operation

The TAP Shift system allows the driver to manually shift gears by using the TAP Shift switches located on the shift lever. Pushing either TAP Shift switch will command an upshift and pulling either switch will command a downshift. The TAP Shift system is activated when the gear selector is placed in the manual (L) position and is deactivated in all other positions.

Transmission General Description

The 4T45-E is a fully automatic front wheel drive electronically controlled transmission. The 4T45-E provides four forward ranges including overdrive and one reverse gear range. The PCM controls shift points by means of 2 shift solenoids. A vane type pump supplies the oil pressure. The PCM regulates oil pressure by means of the pressure control (PC) solenoid.

You can operate the transmission in any one of the following five modes

1. P - Park position prevents the vehicle from rolling either forward or backward. For safety reasons, use the parking brake in addition to the park position.
2. R - Reverse allows the vehicle to be operated in a rearward direction.
3. N - Neutral allows the engine to be started and operated while driving the vehicle. If necessary, you may select this position in order to restart the engine with the vehicle moving.
4. D - Overdrive is used for all normal driving conditions. Overdrive provides four gear ratios plus a converter clutch operation. Depress the accelerator in order to downshift for safe passing.
5. L - Placing the vehicle in this drive position places the vehicle in 3rd gear. This drive position also activates the Driver Shift Control System. The Driver Shift Control System is also referred to as TAP Shift. Refer to «TAP Shift Operation»(/chevrolet/malibu/vii-2008-2012/remont/automatic-trans/#automatic-transaxle-4t45-e-description-and-operation__tap-shift-operation) .

Transmission Component and System Description

The mechanical components of this unit are as follows

1. A torque converter with an electronically controlled capacity clutch (ECCC) This transmission is equipped with an ECCC. The pressure plate does not fully lock to the torque converter cover. Instead, the pressure plate maintains a small amount of slippage, about 20 RPM, in SECOND, THIRD, and FOURTH gears, depending on the vehicle application. ECCC was developed to reduce the possibility of noise, vibration, or chuggle caused by TCC apply. Typical apply speeds are 49-52 km/h (30-32 mph) in THIRD gear and 65-73 km/h (40-45 mph) in FOURTH gear. Full lockup is available at highway speeds on some applications.
2. A drive link assembly
3. Intermediate/4th and Lo/Reverse friction band assemblies
4. Forward, Coast, 2nd, Reverse, and Direct multiple disc clutch assemblies
5. Two planetary gear sets: Input and Reaction
6. Two roller clutches - Lo and 2nd
7. One sprag clutch
8. One vane type oil pump
9. One control valve assembly
10. A final drive and differential assembly

The electrical components of this unit are as follows

1. Two shift solenoid valves, 1-2 and 2-3
2. A torque converter clutch pulse width modulated (TCC PWM) solenoid valve
3. A transmission pressure control (PC) solenoid valve
4. An automatic transmission fluid temperature (TFT) sensor
5. Two speed sensors: input and output speed sensor
6. An automatic transmission fluid pressure (TFP) manual valve position switch assembly
7. An automatic transmission wiring harness assembly
8. A park/neutral position (PNP) switch
9. Floor shift control: includes the electronic range select mode switches

For more information refer to Electronic Component Description .

Transmission Adaptive Functions

The 4T45 automatic transmission uses a line pressure control system, which has the ability to continuously adapt the system line pressure. This compensates for normal wear of the following parts

1. The clutch fiber plates
2. The seals
3. The springs

The transmission control module (TCM) maintains the Upshift Adapt parameters for the transmission. The TCM monitors the input speed sensor (ISS) and the output speed sensor (OSS) during commanded shifts in order to determine if a shift is occurring too fast or too slow. The TCM adjusts the signal from the transmission pressure control (PC) solenoid in order to maintain a set shift feel.

Transmission adapts must be set again when the transmission is overhauled or replaced. In order to set the transmission adapts again, select the following

1. Scan Tool
2. Special Functions
3. Transmission Output Controls
4. Reset Transmission Adapts

Scheme 163

The transmission control module (TCM) is mounted in the engine compartment and connects directly to the engine wiring harness. A single 49-way connector is used to make the connection between the vehicle wiring and the TCM. The TCM is an electronic control module that receives input or provides output in order to control the operation of the 4T45-E automatic transmission.

The TCM receives the following inputs from the engine control module (ECM)

1. Engine speed and torque values
2. Engine intake air temperature (IAT), accelerator pedal position (APP) information
3. Engine coolant temperature (ECT)
4. Kick-down request
5. Traction control status
6. Air-conditioning (A/C) status
7. Cruise control status

The ECM provides this data to the TCM through the controller area network (CAN). The CAN is a 2-wire communication connection between the 2 controllers.

Other TCM inputs are the following

1. Battery and ignition voltage
2. Brake switch status
3. Transmission manual range switch
4. Transmission fluid temperature (TFT)
5. Transmission input speed sensor (ISS)
6. Transmission output speed sensor (OSS)

The TCM provides the following outputs in order to control the automatic transmission

1. Shift solenoids to control transmission shifting
2. TCC PWM solenoid operation to control the apply and release of the torque converter clutch ASM
3. Pressure control solenoid (PCS) to regulate transmission line pressure

Other TCM outputs provided to the ECM are the following

1. MIL illumination request
2. Vehicle speed
3. Transmission input speed
4. Transmission fluid temperature
5. Commanded gear status
6. TCC status
7. Torque reduction requests

Scheme 164

The torque converter clutch (TCC) solenoid valve is a normally closed, pulse width modulated (PWM) solenoid used to control the apply and release of the converter clutch. The TCM operates the solenoid with a negative duty cycle at a fixed frequency of 42 Hz to control the rate of TCC apply/release. The solenoid's ability to ramp the TCC apply and release pressures results in smoother TCC operation.

When vehicle operating conditions are appropriate to apply the TCC, the TCM immediately increases the duty cycle to approximately 42 percent. The TCM then ramps the duty cycle up to approximately 90 percent to achieve full TCC apply pressure. The rate at which the TCM increases the duty cycle controls the TCC apply. Similarly, the TCM also ramps down the TCC solenoid duty cycle to control the TCC release.

Note that the duty cycles in the graph are for example only. Actual duty cycles vary depending on the vehicle application and the vehicle operating conditions.

The TCC solenoid valve resistance should measure between 10-11 ohms when measured at 20°C (68°F). The resistance would measure approximately 16 ohms at 150°C (300°F).

Scheme 165

The pressure control (PC) solenoid valve is a precision electronic pressure regulator that controls the transmission line pressure. This control is based on the flow of current through the coil windings of the valve. As the flow of current is increased, the magnetic field which is produced by the coil moves the solenoid's plunger further away from the exhaust port. Opening the exhaust port decreases the output fluid pressure regulated by the PC solenoid valve, which ultimately decreases line pressure.

The TCM controls the PC solenoid valve based on various inputs, including throttle position, fluid temperature, MAP sensor, and gear state.

The TCM controls the PC solenoid valve on a positive duty cycle at a fixed frequency of 614 Hz. Duty cycle is defined as the percent of time current is flowing through the solenoid coil during each cycle. A higher duty cycle provides a greater current flow through the solenoid. The high, positive, side of the PC solenoid valve electrical circuit at the TCM controls the PC solenoid valve operation. The TCM provides a ground path for the circuit, monitors average current and continuously varies the PC solenoid valve duty cycle to maintain the correct average current flowing through the PC solenoid valve.

The resistance on the PC solenoid valve should measure between 3-5 ohms at 20°C (68°F).

Scheme 166

The shift solenoid valves are two identical, electronic exhaust valves that control upshifts and downshifts in all forward gear ranges. These valves are normally open. These shift solenoid valves work together in a combination of ON and OFF sequences in order to control the positions of the 1-2, 2-3, and 3-4 shift valve trains. The TCM monitors numerous inputs to determine the appropriate solenoid state combination and transmission gear for the vehicle operating conditions.

The TCM energizes the shift solenoid valves by providing a ground to the solenoid's electrical circuit. This sends current through the coil winding of the solenoid, thereby creating a magnetic field. The magnetic field repels the plunger inside the solenoid. This seats the solenoid metering ball against the fluid inlet port. This action prevents the exhaust of fluid through the solenoid. It then provides an increase in fluid pressure at the end of the shift valves. This fluid pressure initiates an upshift by moving the shift valves. Refer to the oil flow diagrams for a complete description of the hydraulic control of the shift valves for each gear range.

The resistance on the shift solenoid valves should measure between 19-24 ohms when measured at 20°C (68°F) and between 24-31 ohms when measured at 88°C (190°F).

The shift solenoid valves should energize when the voltage is greater than 7.5 volts. The shift solenoid valves should de-energize when the voltage is less than one volt.

Scheme 167

The automatic transmission fluid pressure (TFP) manual valve position switch assembly is attached to the control valve body. This assembly contains three fluid pressure switches and the automatic transmission fluid temperature sensor.

Two of the fluid pressure switches are normally-open. These are used to indicate the position of the manual valve. The TCM uses this information to control line pressure, TCC apply and release and shift solenoid operation.

The release pressure switch is used as a diagnostic tool to confirm that the TCC is actually OFF when it has been commanded OFF by the TCM. This switch is normally-closed.

Each fluid pressure switch produces either an open or a ground to the TCM depending on the presence of fluid pressure at the switches. The sequence of open and closed switches produces a combination of voltage readings. The TCM monitors these readings.

The TCM measures TFP manual valve position switch signal voltage from each pin to ground and compares the voltage to a TFP manual valve position switch combination table stored in the TCM memory. If the TCM does not recognize the switch sequence, a diagnostic code will be set as a result. A diagnostic code may also set if the TFP manual valve position switch sequence indicates a gear range selection that conflicts with other sensory inputs to the TCM.

On hybrid applications there is a fourth pressure switch that is normally open. This switch is monitored by the ECM to determine if the transmission has line pressure from either the transmission or the auxiliary transmission pump.

Fluid Pressure and Circuit Combination

Valid combinations for circuits B and C are shown in the table. LOW means that the switch is grounded with a resistance less than 50 ohms at 0 volts; HI means that the switch is open with a resistance greater than 50 K ohms at 12 volts.

Note that resistance should be measured with the engine running. When the transmission's pass through connector is disconnected from the vehicle harness while the engine is running, multiple diagnostic codes will set. Clear these codes when you are finished with this procedure.

Scheme 168

The automatic transmission output speed sensor (OSS) is a magnetic inductive pickup that relays information relative to vehicle speed to the TCM. Vehicle speed information is used by the TCM to control shift timing, line pressure, and TCC apply and release.

The OSS mounts in the case at the speed sensor rotor which is pressed onto the differential. An air gap of 0.27-1.57 mm (0.011-0.062 in) is maintained between the sensor and the teeth on the speed sensor rotor. The sensor consists of a permanent magnet surrounded by a coil of wire. As the differential rotates, an AC signal is induced in the OSS. Higher vehicle speeds induce a higher frequency and voltage measurement at the sensor.

Sensor resistance should be 1500-1650 ohms when measured at 20°C (68°F). Output voltage will vary with speed from a minimum of 0.5 volts AC at 25 RPM to 200 volts AC at 1,728 RPM.

Scheme 169

The automatic transmission input speed sensor (ISS) is a magnetic inductive pickup that relays information about the transmission input speed to the TCM. The TCM uses this information to control the line pressure, TCC apply and release, and the transmission shift patterns. This information is also used to calculate the appropriate operating gear ratios and TCC slippage.

The ISS mounts on the transmission case under the channel plate next to the drive sprocket. An air gap of 0.26-2.90 mm (0.010-0.114 in) is maintained between the sensor and the teeth of the drive sprocket. The sensor consists of a permanent magnet surrounded by a coil of wire. As the drive sprocket is driven by the turbine shaft, an AC signal is induced in the ISS. Higher engine speeds induce a higher frequency and voltage measurement at the sensor.

Sensor resistance should be 625-725 ohms when measured at 20°C (68°F). Output voltage will vary with speed from a minimum of 0.5 volts AC at 550 RPM, to 200 volts AC at 7,000 RPM.

Scheme 170

The automatic transmission fluid temperature (TFT) sensor is a negative temperature coefficient thermistor that provides information to the TCM regarding transmission fluid temperature. The TFT sensor (1) is integrated in the automatic transmission fluid pressure (TFP) manual valve position switch assembly which is bolted to the control valve body. The sensor monitors main line pressure from the inside of the control valve body in order to determine the operating temperature of the transmission fluid. The sensor uses an O-ring seal to maintain fluid pressure in the control valve body.

The internal electrical resistance of the sensor varies in relation to the operating temperature of the transmission fluid. The TCM sends a 5 volt reference signal to the sensor. This measures the voltage drop in the electrical circuit. A lower fluid temperature creates a higher resistance in the TFT sensor, thereby measuring a higher voltage signal.

The TCM measures this voltage as another input to help control line pressure, shift schedules and TCC apply. When the TFT reaches 140°C (284°F), the TCM enters hot mode. Above this temperature the TCM modifies the transmission shift schedules and TCC apply in an attempt to reduce fluid temperature by reducing the amount of heat generated by the transmission. During hot mode the TCM applies TCC at all times in Third and Fourth gears. Also, the TCM performs the 2-3 and the 3-4 shifts earlier in order to help reduce the generation of fluid heat. Refer to Transmission Fluid Temperature Sensor Specifications .

Scheme 171

The transmission range (TR) switch is part of the park/neutral position (PNP) and back-up lamp switch assembly, which is externally mounted on the transmission manual shaft. The TR switch contains four internal switches that indicate the transmission gear range selector lever position. The TCM supplies ignition voltage to each switch circuit. By grounding one or more of the switch circuits, the TCM detects the selected gear range by the state change of the switch input. Refer to Transmission Range Switch Logic . Switch input to the TCM is represented on the scan tool as HI and LOW. HI indicates an ignition voltage signal. LOW indicates a zero voltage signal. The four parameters represent transmission range switch signal A, B, C and Parity.

Scheme 172

The floor shift control is located in the center console assembly. It contains the upshift and downshift switches for the electronic range select mode system. The electronic range select mode system is activated when the floor shift control lever is moved to the right into the Low (L) position from the drive position. When the manual position is selected, an upshift is requested by pushing the upshift switch on the floor shift control lever and a downshift is requested by pushing the downshift switch on the floor shift control lever. When an upshift or a downshift is requested, a signal is sent to the TCM which commands the shift solenoids ON or OFF to achieve the appropriate gear.

Park - Engine Running (W/O Electronic Range Select Mode)

When the gear selector lever is in the Park (P) position and the engine is running, fluid is drawn into the oil pump. Line pressure is directed to the pressure regulator valve.

Pressure Regulator Valve

The pressure regulator valve regulates the pump output (line pressure) in response to a torque signal fluid pressure, which acts on the boost valve, the spring force, and the line pressure acting on the end of the valve. Line pressure is directed to the manual valve, to both accumulator valves, to the torque signal regulator valve, to the TCC regulated apply valve, to the temperature sensor in the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.), and to the actuator feed limit valve. Also, line pressure feeds the converter feed fluid circuit through the pressure regulator valve.

Actuator Feed Limit (AFL) Valve

Line pressure is routed through the valve and into the actuator feed fluid circuit. The valve limits the actuator feed fluid pressure to a maximum pressure. Actuator feed fluid is routed to the pressure control solenoid and to each of the shift valves. The fluid also feeds the 1-2 signal and the 2-3 signal fluid circuits.

Pressure Control Solenoid (PCS) Valve

Controlled by the PCM, the PCS valve regulates the filtered actuator feed fluid pressure which acts on the end of the torque signal regulating valve.

Torque Signal Regulating Valve

Note. Actuator feed fluid continues to feed the 2-3 signal fluid circuit through orifice #6. However, the exhaust port through the 2-3 shift solenoid valve is larger that orifice #6 in order to prevent a pressure increase in the 2-3 signal fluid circuit.

The torque signal regulating valve regulates the line pressure into the torque signal fluid circuit. Filtered actuator feed fluid pressure from the PCS controls this regulation. torque signal fluid pressure is routed to the accumulator valves and to the boost valve in order to control shift feel.

Manual Valve

The gear selector lever mechanically controls the manual valve, which is in Park (P) position. The manual valve directs line pressure into the PRND4 and the PRN fluid circuits.

Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) Assembly

PRND4 fluid is routed to the PRND4 fluid pressure switch in the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in the Park (P) position. Line pressure is routed to the A/T Fluid Temperature Sensor in the TFP Val. Position Sw. Assembly.

1-2 Shift Solenoid Valve

Energized by the PCM, the normally open 1-2 shift solenoid valve is On and blocks the 1-2 signal fluid from exhausting. The 1-2 signal fluid pressure acts on the 1-2 and the 3-4 shift valves.

1-2 Shift Valve

The 1-2 signal fluid pressure holds the valve in the downshifted position against a spring force. Low/PRN fluid is routed through the 1-2 shift valve and into the Low band fluid circuit.

Low and Reverse Servo

Low band fluid is routed to the inner area of the servo piston. Low band fluid pressure moves the servo piston and pin assembly against a spring force in order to apply the low/reverse band.

2-3 Shift Solenoid Valve

The normally open 2-3 shift solenoid is Off and the 2-3 signal fluid is exhausted through the solenoid.

2-3 Shift Valve

A spring force holds the 2-3 shift valve in the downshifted position.

3-4 Shift Valve

The 1-2 signal fluid pressure holds the 3-4 shift valve against a spring force in the First and the Fourth gear positions.

Lube 2

The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission.

1-2/3-4 Accumulator Valves

Line pressure is regulated into accumulator fluid pressure. Torque signal fluid pressure acting on the end of the valve basically controls this regulation.

1-2, and 3-4 Accumulator Assemblies

Accumulator fluid is routed to each of the accumulator assemblies in preparation for upshifts. The fluid which is routed to the 1-2 and to the 3-4 accumulators is orificed by the #4 and the #7 checkballs. The 2-3 accumulator fluid circuit does not use a checkball in order to orifice accumulator fluid to the 2-3 accumulator.

Torque Converter/Cooler and Lube Circuits

Refer to reverse range for a complete description of these circuits.

Scheme 173

Park - Engine Running (With Electronic Range Select Mode)

When the gear selector lever is in the Park (P) position and the engine is running, fluid is drawn into the oil pump. Line pressure is directed to the pressure regulator valve.

The pressure regulator valve regulates the pump output (line pressure) in response to a torque signal fluid pressure, which acts on the boost valve, the spring force, and the line pressure acting on the end of the valve. Line pressure is directed to the manual valve, to both accumulator valves, to the torque signal regulator valve, to the TCC regulated apply valve, to the temperature sensor in the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.), and to the actuator feed limit valve. Also, line pressure feeds the converter feed fluid circuit through the pressure regulator valve.

Line pressure is routed through the valve and into the actuator feed fluid circuit. The valve limits the actuator feed fluid pressure to a maximum pressure. Actuator feed fluid is routed to the pressure control solenoid and to each of the shift valves. The fluid also feeds the 1-2 signal and the 2-3 signal fluid circuits.

Controlled by the PCM, the PCS valve regulates the filtered actuator feed fluid pressure which acts on the end of the torque signal regulating valve.

Note. Actuator feed fluid continues to feed the 2-3 signal fluid circuit through orifice #6. However, the exhaust port through the 2-3 shift solenoid valve is larger that orifice #6 in order to prevent a pressure increase in the 2-3 signal fluid circuit.

The torque signal regulating valve regulates the line pressure into the torque signal fluid circuit. Filtered actuator feed fluid pressure from the PCS controls this regulation. torque signal fluid pressure is routed to the accumulator valves and to the boost valve in order to control shift feel.

The gear selector lever mechanically controls the manual valve, which is in Park (P) position. The manual valve directs line pressure into the PRND4 and the PRN fluid circuits.

PRND4 fluid is routed to the PRND4 fluid pressure switch in the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in the Park (P) position. Line pressure is routed to the A/T Fluid Temperature Sensor in the TFP Val. Position Sw. Assembly.

Energized by the PCM, the normally open 1-2 shift solenoid valve is On and blocks the 1-2 signal fluid from exhausting. The 1-2 signal fluid pressure acts on the 1-2 and the 3-4 shift valves.

The 1-2 signal fluid pressure holds the valve in the downshifted position against a spring force. Low/PRN fluid is routed through the 1-2 shift valve and into the Low band fluid circuit.

Low band fluid is routed to the inner area of the servo piston. Low band fluid pressure moves the servo piston and pin assembly against a spring force in order to apply the low/reverse band. The low band fluid is routed to the 3-4 shift valve. The pressure moves the valve against 1-2 signal fluid.

The normally open 2-3 shift solenoid is Off and the 2-3 signal fluid is exhausted through the solenoid.

A spring force holds the 2-3 shift valve in the downshifted position.

The 1-2 signal fluid pressure holds the 3-4 shift valve against a spring force in the First and the Fourth gear positions.

The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission.

Line pressure is regulated into accumulator fluid pressure. Torque signal fluid pressure acting on the end of the valve basically controls this regulation.

Accumulator fluid is routed to each of the accumulator assemblies in preparation for upshifts. The fluid which is routed to the 1-2 and to the 3-4 accumulators is orificed by the #4 and the #7 checkballs. The 2-3 accumulator fluid circuit does not use a checkball in order to orifice accumulator fluid to the 2-3 accumulator.

Torque Converter

Release fluid pressure is routed to the torque converter inorder to keep the Tcc released. Fluid leaves the converter in the apply fluid circuit.

Lube 1

Cooler fluid is routed through the transmission oil cooler, which is located in the vehicle radiator, and into the lube 1 fluid circuit. Lube 1 fluid is routed through the input shaft in order to lubricate the transmission components in the front of the transmission.

The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission. The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve.

Scheme 174

Park - Engine Running (L4 Hybrid)

When the gear selector lever is in the Park (P) position and the engine is running, fluid is drawn into the oil pump. Line pressure is directed to the pressure regulator valve.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

The pressure regulator valve regulates the pump output (line pressure) in response to a torque signal fluid pressure, which acts on the boost valve, the spring force, and the line pressure acting on the end of the valve. Line pressure is directed to the manual valve, to both accumulator valves, to the torque signal regulator valve, to the TCC regulated apply valve, to the temperature sensor in the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.), and to the actuator feed limit valve. Also, line pressure feeds the converter feed fluid circuit through the pressure regulator valve.

Line pressure is routed through the valve and into the actuator feed fluid circuit. The valve limits the actuator feed fluid pressure to a maximum pressure. Actuator feed fluid is routed to the pressure control solenoid and to each of the shift valves. The fluid also feeds the 1-2 signal and the 2-3 signal fluid circuits.

Controlled by the PCM, the PCS valve regulates the filtered actuator feed fluid pressure which acts on the end of the torque signal regulating valve.

Note. Actuator feed fluid continues to feed the 2-3 signal fluid circuit through orifice #6. However, the exhaust port through the 2-3 shift solenoid valve is larger that orifice #6 in order to prevent a pressure increase in the 2-3 signal fluid circuit.

The torque signal regulating valve regulates the line pressure into the torque signal fluid circuit. Filtered actuator feed fluid pressure from the PCS controls this regulation. torque signal fluid pressure is routed to the accumulator valves and to the boost valve in order to control shift feel.

The gear selector lever mechanically controls the manual valve, which is in Park (P) position. The manual valve directs line pressure into the PRND4 and the PRN fluid circuits.

PRND4 fluid is routed to the PRND4 fluid pressure switch in the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in the Park (P) position. Line pressure is routed to the A/T Fluid Temperature Sensor in the TFP Val. Position Sw. Assembly.

Energized by the PCM, the normally open 1-2 shift solenoid valve is On and blocks the 1-2 signal fluid from exhausting. The 1-2 signal fluid pressure acts on the 1-2 and the 3-4 shift valves.

The 1-2 signal fluid pressure holds the valve in the downshifted position against a spring force. Low/PRN fluid is routed through the 1-2 shift valve and into the Low band fluid circuit.

Low band fluid is routed to the inner area of the servo piston. Low band fluid pressure moves the servo piston and pin assembly against a spring force in order to apply the low/reverse band. The low band fluid is routed to the 3-4 shift valve. The pressure moves the valve against 1-2 signal fluid.

The normally open 2-3 shift solenoid is Off and the 2-3 signal fluid is exhausted through the solenoid.

A spring force holds the 2-3 shift valve in the downshifted position.

The 1-2 signal fluid pressure holds the 3-4 shift valve against a spring force in the First and the Fourth gear positions.

The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission.

Line pressure is regulated into accumulator fluid pressure. Torque signal fluid pressure acting on the end of the valve basically controls this regulation.

Accumulator fluid is routed to each of the accumulator assemblies in preparation for upshifts. The fluid which is routed to the 1-2 and to the 3-4 accumulators is orificed by the #4 and the #7 checkballs. The 2-3 accumulator fluid circuit does not use a checkball in order to orifice accumulator fluid to the 2-3 accumulator.

Refer to Reverse (W/O Electronic Range Select Mode) or Reverse (With Electronic Range Select Mode) or Reverse (L4 Hybrid) for a complete description of these circuits.

Scheme 175

Reverse (W/O Electronic Range Select Mode)

Note. The explanation of each gear range is primarily limited to those changes from the previous range. However, some component descriptions are repeated for clarity and continuity.

When you move the gear selector lever to the Reverse (R) position (from the Park position), the following changes occur in the transmission's hydraulic and electrical systems.

With the manual valve in the reverse position, line pressure is directed into the reverse fluid circuit, in addition to the PRND4 and the PRN fluid circuits, which were used in Park position.

Pressure Regulator and Boost Valves

Reverse fluid is routed to the boost valve. Reverse fluid assists torque signal fluid pressure. The addition of reverse fluid pressure increases the operating range of the line pressure in Reverse position.

A/T Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) Assembly

Reverse fluid is routed through the 1-2 shift valve and to the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in Reverse position.

Reverse Clutch

Reverse clutch fluid pressure applies the reverse clutch.

The PCM keeps the solenoid valve energized in Reverse position. The 1-2 signal fluid pressure acts on the 1-2 shift valve.

The 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position. Low/PRN fluid continues to feed the low band fluid circuit.

Reverse fluid is routed to the outer area of the servo in order to increase the servo apply pressure in the Reverse position.

Pressure Regulator (PR) Valve

Line pressure is routed through the PR valve and into the converter feed fluid circuit. Converter feed fluid is routed to the TCC feed limit valve.

TCC Feed Limit Valve

Converter feed fluid is routed through the valve and into the TCC feed limit fluid circuit.

TCC Regulated Apply Valve

A spring force holds the valve in the release position, thereby blocking line pressure.

TCC Control Valve

A spring force holds the valve in the release position. TCC feed limit fluid is routed into the release fluid circuit. Fluid returns from the converter in the apply fluid circuit. This fluid is routed through the valve and into the cooler fluid circuit.

Release fluid pressure is routed to the torque converter in order to keep the TCC released. Fluid leaves the converter in the apply fluid circuit.

Cooler fluid is routed through the transmission oil cooler, which is located in the vehicle radiator, and into the lube 1 fluid circuit. Lube 1 fluid is routed through the input shaft in order to lubricate the transmission components in the front of the transmission.

The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission. The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission.

Scheme 176

Reverse (With Electronic Range Select Mode)

Note. The explanation of each gear range is primarily limited to those changes from the previous range. However, some component descriptions are repeated for clarity and continuity.

When you move the gear selector lever to the Reverse (R) position (from the Park position), the following changes occur in the transmission's hydraulic and electrical systems.

With the manual valve in the reverse position, line pressure is directed into the reverse fluid circuit, in addition to the PRND4 and the PRN fluid circuits, which were used in Park position.

Reverse fluid is routed to the boost valve. Reverse fluid assists torque signal fluid pressure. The addition of reverse fluid pressure increases the operating range of the line pressure in Reverse position.

Reverse fluid is routed through the 1-2 shift valve and to the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in Reverse position.

Reverse clutch fluid pressure applies the reverse clutch.

The PCM keeps the solenoid valve energized in Reverse position. The 1-2 signal fluid pressure acts on the 1-2 shift valve.

The 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position. Low/PRN fluid continues to feed the low band fluid circuit.

Reverse fluid is routed to the outer area of the servo in order to increase the servo apply pressure in the Reverse position. The low band fluid is routed to the 3-4 shift valve. The pressure moves the 3-4 shift valve against the 1-2 signal fluid.

Line pressure is routed through the PR valve and into the converter feed fluid circuit. Converter feed fluid is routed to the TCC feed limit valve.

Converter feed fluid is routed through the valve and into the TCC feed limit fluid circuit.

A spring force holds the valve in the release position, thereby blocking line pressure.

A spring force holds the valve in the release position. TCC feed limit fluid is routed into the release fluid circuit. Fluid returns from the converter in the apply fluid circuit. This fluid is routed through the valve and into the cooler fluid circuit.

Release fluid pressure is routed to the torque converter in order to keep the TCC released. Fluid leaves the converter in the apply fluid circuit.

Cooler fluid is routed through the transmission oil cooler, which is located in the vehicle radiator, and into the lube 1 fluid circuit. Lube 1 fluid is routed through the input shaft in order to lubricate the transmission components in the front of the transmission.

The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission. The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission.

Scheme 177

Reverse (L4 Hybrid)

Note. The explanation of each gear range is primarily limited to those changes from the previous range. However, some component descriptions are repeated for clarity and continuity. Also, refer to the appropriate General Motors Service manual for specific application information.

When you move the gear selector lever to the Reverse (R) position (from the Park position), the following changes occur in the transmission's hydraulic and electrical systems.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

With the manual valve in the reverse position, line pressure is directed into the reverse fluid circuit, in addition to the PRND4 and the PRN fluid circuits, which were used in Park position.

Reverse fluid is routed to the boost valve. Reverse fluid assists torque signal fluid pressure. The addition of reverse fluid pressure increases the operating range of the line pressure in Reverse position.

Reverse fluid is routed through the 1-2 shift valve and to the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in Reverse position.

Reverse clutch fluid pressure applies the reverse clutch.

The PCM keeps the solenoid valve energized in Reverse position. The 1-2 signal fluid pressure acts on the 1-2 shift valve.

The 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position. Low/PRN fluid continues to feed the low band fluid circuit.

Reverse fluid is routed to the outer area of the servo in order to increase the servo apply pressure in the Reverse position. The low band fluid is routed to the 3-4 shift valve. The pressure moves the 3-4 shift valve against the 1-2 signal fluid.

Line pressure is routed through the PR valve and into the converter feed fluid circuit. Converter feed fluid is routed to the TCC feed limit valve.

Converter feed fluid is routed through the valve and into the TCC feed limit fluid circuit.

A spring force holds the valve in the release position, thereby blocking line pressure.

A spring force holds the valve in the release position. TCC feed limit fluid is routed into the release fluid circuit. Fluid returns from the converter in the apply fluid circuit. This fluid is routed through the valve and into the cooler fluid circuit.

Release fluid pressure is routed to the torque converter in order to keep the TCC released. Fluid leaves the converter in the apply fluid circuit.

Cooler fluid is routed through the transmission oil cooler, which is located in the vehicle radiator, and into the lube 1 fluid circuit. Lube 1 fluid is routed through the input shaft in order to lubricate the transmission components in the front of the transmission.

The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission. The lube 2 fluid circuit is fed by line pressure at the pressure regulator valve. Lube 2 fluid is routed through the oil feed pipes and into the forward clutch support. Lube 2 fluid provides lubrication in the rear of the transmission.

Scheme 178

Neutral - Engine Running (W/O Electronic Range Select Mode)

When you move the gear selector lever from the Reverse position to the Neutral position, the following changes occur to the hydraulic and electrical systems.

The manual valve is moved to the Neutral position, where the valve blocks the line pressure from entering the Reverse fluid circuit. The reverse fluid circuit is opened to an exhaust at the manual valve.

Reverse fluid exhausts from the reverse clutch and the clutch releases. This action shifts the transmission in to Neutral position.

Boost Valve

Reverse fluid exhausts from the boost valve and line pressure regulation returns to the normal operating range.

Reverse fluid pressure exhausts from the TFP Val. Position Sw. Assembly. This action signals the PCM that the transmission is either in Neutral (N) or Park (P) position.

Low and Reverse Band Remains Applied

Note. In Park, Reverse, and Neutral positions the shift solenoid valves are shown to be in the First gear state. this is the normal operating state when the vehicle is stationary or at low vehicle speeds. However, the PCM will change the shift solenoid valve states depending on the speed of the vehicle. For example, if the Neutral range is selected when the vehicle is operating in Second gear, the shift solenoid valves will remain in a Second gear state. But with the manual valve in Neutral, line pressure is blocked, drive fluid exhausts and the transmission will shift into Neutral.

As in Park and Reverse positions, the solenoid valve is energized and 1-2 signal fluid pressure acts on the 1-2 shift valve.

The 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position. Low/PRN fluid continues to feed the low band fluid circuit.

Reverse fluid exhausts from the servo. However, low band fluid pressure continues to act on the inner area of the servo piston in order to keep the band applied.

Scheme 179

Neutral - Engine Running (With Electronic Range Select Mode)

When you move the gear selector lever from the Reverse position to the Neutral position, the following changes occur to the hydraulic and electrical systems.

The manual valve is moved to the Neutral position, where the valve blocks the line pressure from entering the Reverse fluid circuit. The reverse fluid circuit is opened to an exhaust at the manual valve.

Reverse fluid exhausts from the reverse clutch and the clutch releases. This action shifts the transmission in to Neutral position.

Reverse fluid exhausts from the boost valve and line pressure regulation returns to the normal operating range.

Reverse fluid pressure exhausts from the TFP Val. Position Sw. Assembly. This action signals the PCM that the transmission is either in Neutral (N) or Park (P) position.

Note. In Park, Reverse, and Neutral positions the shift solenoid valves are shown to be in the First gear state. this is the normal operating state when the vehicle is stationary or at low vehicle speeds. However, the PCM will change the shift solenoid valve states depending on the speed of the vehicle. For example, if the Neutral range is selected when the vehicle is operating in Second gear, the shift solenoid valves will remain in a Second gear state. But with the manual valve in Neutral, line pressure is blocked, drive fluid exhausts and the transmission will shift into Neutral.

As in Park and Reverse positions, the solenoid valve is energized and 1-2 signal fluid pressure acts on the 1-2 shift valve.

The 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position. Low/PRN fluid continues to feed the low band fluid circuit.

Reverse fluid exhausts from the servo. However, low band fluid pressure continues to act on the inner area of the servo piston in order to keep the band applied.

Scheme 180

Overdrive Range, First Gear (W/O Electronic Range Select Mode)

When you move the gear selector lever to the Overdrive (D) position from the Neutral (N) position, the following changes occur in order to shift the transmission into Overdrive Range - First Gear.

In the Overdrive position, the manual valve directs line pressure into the drive fluid circuit. The manual valve blocks line pressure from entering the PRN fluid circuit and the manual valve opens the PRN fluid circuit in order to exhaust.

Low band fluid pressure exhausts from the servo, releasing the servo and the low and reverse band.

Forward Clutch

Drive fluid is orificed into the forward clutch fluid circuit. Forward clutch fluid pressure applies the forward clutch.

In first gear, the PCM energizes the 1-2 shift solenoid valve and the 1-2 signal fluid pressure acts on the 1-2 shift valve.

The 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position against a spring force. Drive fluid is routed through the 1-2 shift valve.

Drive fluid is routed to the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in the Overdrive range.

Scheme 181

Overdrive Range, First Gear (With Electronic Range Select Mode)

When you move the gear selector lever to the Overdrive (D) position from the Neutral (N) position, the following changes occur in order to shift the transmission into Overdrive Range - First Gear.

In the Overdrive position, the manual valve directs line pressure into the drive fluid circuit. The manual valve blocks line pressure from entering the PRN fluid circuit and the manual valve opens the PRN fluid circuit in order to exhaust.

Low band fluid pressure exhausts from the servo, releasing the servo and the low and reverse band.

Drive fluid is orificed into the forward clutch fluid circuit. Forward clutch fluid pressure applies the forward clutch.

In first gear, the PCM energizes the 1-2 shift solenoid valve and the 1-2 signal fluid pressure acts on the 1-2 shift valve.

The 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position against a spring force. Drive fluid is routed through the 1-2 shift valve.

Drive fluid is routed to the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in the Overdrive range.

Scheme 182

Overdrive Range, First Gear (L4 Hybrid)

When you move the gear selector lever to the Overdrive (D) position from the Neutral (N) position, the following changes occur in order to shift the transmission into Overdrive Range - First Gear.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

In the Overdrive position, the manual valve directs line pressure into the drive fluid circuit. The manual valve blocks line pressure from entering the PRN fluid circuit and the manual valve opens the PRN fluid circuit in order to exhaust.

Low band fluid pressure exhausts from the servo, releasing the servo and the low and reverse band.

Drive fluid is orificed into the forward clutch fluid circuit. Forward clutch fluid pressure applies the forward clutch.

In first gear, the PCM energizes the 1-2 shift solenoid valve and the 1-2 signal fluid pressure acts on the 1-2 shift valve.

The 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position against a spring force. Drive fluid is routed through the 1-2 shift valve.

Drive fluid is routed to the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in the Overdrive range.

Scheme 183

Overdrive Range, Second Gear (W/O Electronic Range Select Mode)

As vehicle speed increases and operating conditions become appropriate, the PCM de-energizes the 1-2 shift solenoid valve in order to shift the transmission into Second gear. The manual valve remains in the Overdrive (D) position and line pressure is routed into the drive and PRND4 fluid circuits.

The normally open shift solenoid valve is de-energized and 1-2 signal fluid exhausts through the open valve.

Note. Filtered actuator feed fluid continues to feed the 1-2 signal fluid circuit through orifice #7. However, the exhaust port through the solenoid is larger than orifice #7 in order to prevent a pressure increase in the 1-2 signal fluid circuit.

With 1-2 signal fluid pressure exhausted, a spring force moves the valve into the upshifted position. Drive fluid is routed into the 2-3 drive fluid circuit. Drive fluid also continues to flow through the valve and to the A/T Fluid Pressure Manual Valve Position Switch.

#2 Checkball (Second Clutch Apply)

The 2-3 drive fluid seats the #2 checkball, forcing the 2-3 drive fluid through the #3 orifice and feeding the second clutch fluid circuit. the #3 and the #4 orifices help to control the apply feel of the second clutch.

Second Clutch

The second clutch fluid pressure applies the second clutch, which shifts the transmission into Second gear.

1-2 Accumulator

Second clutch fluid is also routed to the 1-2 accumulator piston. A combination of second clutch fluid pressure and the 1-2 assist spring force moves the piston against this spring force and the 1-2 accumulator feed fluid pressure. This action absorbs the initial second clutch fluid pressure in order to cushion the second clutch apply. The movement of the 1-2 accumulator piston forces some of the fluid out of the accumulator.

1-2 Accumulator Valve

The 1-2 accumulator feed fluid which is forced from the 1-2 accumulator unseats the #4 checkball. This fluid is then routed back to the 1-2 accumulator valve. This pressure forces the 1-2 accumulator valve against a combination of spring force and torque signal fluid pressure in order to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the second clutch apply.

TCC Control - Pulse Width Modulated (PWM) Solenoid Valve

Filtered 2-3 drive fluid is routed to the TCC control solenoid valve. Under normal operating conditions the TCC control solenoid valve is Off in Second gear. This valve blocks filtered 2-3 drive fluid from entering the TCC signal fluid circuit.

Torque Converter Clutch

With the TCC control solenoid valve Off, the converter clutch is released in Second gear.

The 2-3 shift solenoid valve remains Off in Second gear, and the 2-3 signal fluid exhausts through the normally open solenoid valve.

A spring force keeps the 2-3 shift valve in the downshifted position. In this position the valve blocks 2-3 drive fluid, in preparation for the upshift into Third gear.

Scheme 184

Overdrive Range, Second Gear (With Electronic Range Select Mode)

As vehicle speed increases and operating conditions become appropriate, the PCM de-energizes the 1-2 shift solenoid valve in order to shift the transmission into Second gear. The manual valve remains in the Overdrive (D) position and line pressure is routed into the drive and PRND4 fluid circuits.

The normally open shift solenoid valve is de-energized and 1-2 signal fluid exhausts through the open valve.

Note. Filtered actuator feed fluid continues to feed the 1-2 signal fluid circuit through orifice #7. However, the exhaust port through the solenoid is larger than orifice #7 in order to prevent a pressure increase in the 1-2 signal fluid circuit.

With 1-2 signal fluid pressure exhausted, a spring force moves the valve into the upshifted position. Drive fluid is routed into the 2-3 drive fluid circuit. Drive fluid also continues to flow through the valve and to the A/T Fluid Pressure Manual Valve Position Switch.

The 2-3 drive fluid seats the #2 checkball, forcing the 2-3 drive fluid through the #3 orifice and feeding the second clutch fluid circuit. the #3 and the #4 orifices help to control the apply feel of the second clutch.

The second clutch fluid pressure applies the second clutch, which shifts the transmission into Second gear.

Second clutch fluid is also routed to the 1-2 accumulator piston. A combination of second clutch fluid pressure and the 1-2 assist spring force moves the piston against this spring force and the 1-2 accumulator feed fluid pressure. This action absorbs the initial second clutch fluid pressure in order to cushion the second clutch apply. The movement of the 1-2 accumulator piston forces some of the fluid out of the accumulator.

The 1-2 accumulator feed fluid which is forced from the 1-2 accumulator unseats the #4 checkball. This fluid is then routed back to the 1-2 accumulator valve. This pressure forces the 1-2 accumulator valve against a combination of spring force and torque signal fluid pressure in order to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the second clutch apply.

Filtered 2-3 drive fluid is routed to the TCC control solenoid valve. Under normal operating conditions the TCC control solenoid valve is Off in Second gear. This valve blocks filtered 2-3 drive fluid from entering the TCC signal fluid circuit.

With the TCC control solenoid valve Off, the converter clutch is released in Second gear.

The 2-3 shift solenoid valve remains Off in Second gear, and the 2-3 signal fluid exhausts through the normally open solenoid valve.

A spring force keeps the 2-3 shift valve in the downshifted position. In this position the valve blocks 2-3 drive fluid, in preparation for the upshift into Third gear.

Scheme 185

Overdrive Range, Second Gear (L4 Hybrid)

As vehicle speed increases and operating conditions become appropriate, the PCM de-energizes the 1-2 shift solenoid valve in order to shift the transmission into Second gear. The manual valve remains in the Overdrive (D) position and line pressure is routed into the drive and PRND4 fluid circuits.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

The normally open shift solenoid valve is de-energized and 1-2 signal fluid exhausts through the open valve.

Note. Filtered actuator feed fluid continues to feed the 1-2 signal fluid circuit through orifice #7. However, the exhaust port through the solenoid is larger than orifice #7 in order to prevent a pressure increase in the 1-2 signal fluid circuit.

With 1-2 signal fluid pressure exhausted, a spring force moves the valve into the upshifted position. Drive fluid is routed into the 2-3 drive fluid circuit. Drive fluid also continues to flow through the valve and to the A/T Fluid Pressure Manual Valve Position Switch.

The 2-3 drive fluid seats the #2 checkball, forcing the 2-3 drive fluid through the #3 orifice and feeding the second clutch fluid circuit. The #3 and the #4 orifices help to control the apply feel of the second clutch.

The second clutch fluid pressure applies the second clutch, which shifts the transmission into Second gear.

Second clutch fluid is also routed to the 1-2 accumulator piston. A combination of second clutch fluid pressure and the 1-2 assist spring force moves the piston against this spring force and the 1-2 accumulator feed fluid pressure. This action absorbs the initial second clutch fluid pressure in order to cushion the second clutch apply. The movement of the 1-2 accumulator piston forces some of the fluid out of the accumulator.

The 1-2 accumulator feed fluid which is forced from the 1-2 accumulator unseats the #4 checkball. This fluid is then routed back to the 1-2 accumulator valve. This pressure forces the 1-2 accumulator valve against a combination of spring force and torque signal fluid pressure in order to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the second clutch apply.

Filtered 2-3 drive fluid is routed to the TCC control solenoid valve. Under normal operating conditions the TCC control solenoid valve is Off in Second gear. This valve blocks filtered 2-3 drive fluid from entering the TCC signal fluid circuit.

With the TCC control solenoid valve Off, the converter clutch is released in Second gear.

The 2-3 shift solenoid valve remains Off in Second gear, and the 2-3 signal fluid exhausts through the normally open solenoid valve.

A spring force keeps the 2-3 shift valve in the downshifted position. In this position the valve blocks 2-3 drive fluid, in preparation for the upshift into Third gear.

Scheme 186

Overdrive Range, Third Gear - Torque Converter Clutch Not Applied (W/O Electronic Range Select Mode)

As vehicle speed increases and operating conditions become appropriate, the PCM energized the 2-3 shift solenoid valve in order to shift the transmission into Third gear. The manual valve remains in the Overdrive (D) position, and line pressure continues to feed the drive and the PRND4 fluid circuits.

The PCM energizes the normally open 2-3 shift solenoid valve, which blocks the 2-3 signal fluid from exhausting. The 2-3 signal fluid pressure is routed to both of the 1-2 and 2-3 shift valves.

The 2-3 signal fluid pressure moves the valve against a spring force in order to initiate the 2-3 upshift. The 2-3 drive fluid is routed through the valve and into the 3-4 drive fluid circuit.

#5 Checkball (Direct Clutch Apply)

The 3-4 drive fluid pressure seats the #5 checkball, and 3-4 drive fluid is forced through the #26 orifice and into the direct clutch feed fluid circuit. the #26 orifice helps to control the direct clutch apply.

Direct Clutch

The direct clutch fluid pressure applies the direct clutch, causing the transmission to shifts into Third gear.

The 3-4 drive fluid is also routed to the 3-4 shift valve in preparation for a 3-4 upshift.

2-3 Accumulator

Direct clutch feed fluid is also routed to the 2-3 accumulator piston. This fluid pressure moves the piston against a combination of spring force and the 2-3 accumulator feed fluid pressure. This action absorbs the initial direct clutch fluid pressure in order to cushion the direct clutch apply. the movement of the 2-3 accumulator piston forces some of the fluid out of the accumulator.

Torque Converter Clutch (TCC)

Torque Converter Clutch (TCC) Under normal operating conditions the TCC is released in Third gear. However the TCC apply could vary depending upon the vehicle application, and the TCC may be calibrated in order to apply in Overdrive Range - Third gear.

Release fluid pressure routed to the TFP Val. Position Sw. Assembly signals to the PCM that the TCC is released.

Scheme 187

Overdrive Range, Third Gear - Torque Converter Clutch Not Applied (With Electronic Range Select Mode)

As vehicle speed increases and operating conditions become appropriate, the PCM energized the 2-3 shift solenoid valve in order to shift the transmission into Third gear. The manual valve remains in the Overdrive (D) position, and line pressure continues to feed the drive and the PRND4 fluid circuits.

The PCM energizes the normally open 2-3 shift solenoid valve, which blocks the 2-3 signal fluid from exhausting. The 2-3 signal fluid pressure is routed to both of the 1-2 and 2-3 shift valves.

The 2-3 signal fluid pressure moves the valve against a spring force in order to initiate the 2-3 upshift. The 2-3 drive fluid is routed through the valve and into the 3-4 drive fluid circuit.

The 3-4 drive fluid pressure seats the #5 checkball, and 3-4 drive fluid is forced through the #26 orifice and into the direct clutch feed fluid circuit. The #26 orifice helps to control the direct clutch apply.

The direct clutch fluid pressure applies the direct clutch, causing the transmission to shifts into Third gear.

The 3-4 drive fluid is also routed to the 3-4 shift valve in preparation for a 3-4 upshift.

Direct clutch feed fluid is also routed to the 2-3 accumulator piston. This fluid pressure moves the piston against a combination of spring force and the 2-3 accumulator feed fluid pressure. This action absorbs the initial direct clutch fluid pressure in order to cushion the direct clutch apply. the movement of the 2-3 accumulator piston forces some of the fluid out of the accumulator.

Torque Converter Clutch (TCC) Under normal operating conditions the TCC is released in Third gear. However the TCC apply could vary depending upon the vehicle application, and the TCC may be calibrated in order to apply in Overdrive Range - Third gear.

Release fluid pressure routed to the TFP Val. Position Sw. Assembly signals to the PCM that the TCC is released.

Scheme 188

Overdrive Range, Third Gear - Torque Converter Clutch Not Applied (L4 Hybrid)

As vehicle speed increases and operating conditions become appropriate, the PCM energized the 2-3 shift solenoid valve in order to shift the transmission into Third gear. The manual valve remains in the Overdrive (D) position, and line pressure continues to feed the drive and the PRND4 fluid circuits.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

The PCM energizes the normally open 2-3 shift solenoid valve, which blocks the 2-3 signal fluid from exhausting. The 2-3 signal fluid pressure is routed to both of the 1-2 and 2-3 shift valves.

The 2-3 signal fluid pressure moves the valve against a spring force in order to initiate the 2-3 upshift. The 2-3 drive fluid is routed through the valve and into the 3-4 drive fluid circuit.

The 3-4 drive fluid pressure seats the #5 checkball, and 3-4 drive fluid is forced through the #26 orifice and into the direct clutch feed fluid circuit. the #26 orifice helps to control the direct clutch apply.

The direct clutch fluid pressure applies the direct clutch, causing the transmission to shifts into Third gear.

The 3-4 drive fluid is also routed to the 3-4 shift valve in preparation for a 3-4 upshift.

Direct clutch feed fluid is also routed to the 2-3 accumulator piston. This fluid pressure moves the piston against a combination of spring force and the 2-3 accumulator feed fluid pressure. This action absorbs the initial direct clutch fluid pressure in order to cushion the direct clutch apply. the movement of the 2-3 accumulator piston forces some of the fluid out of the accumulator.

Torque Converter Clutch (TCC) Under normal operating conditions the TCC is released in Third gear. However the TCC apply could vary depending upon the vehicle application, and the TCC may be calibrated in order to apply in Overdrive Range - Third gear.

Release fluid pressure routed to the TFP Val. Position Sw. Assembly signals to the PCM that the TCC is released.

Scheme 189

Overdrive Range, Fourth Gear - Torque Converter Clutch Applied (W/O Electronic Range Select Mode)

When operating conditions are appropriate, the PCM energizes the 1-2 shift solenoid valve in order to shift the transmission into Fourth gear. In addition, the TCC is applied in Fourth gear. The manual valve remains in the Overdrive position and line pressure continues to feed the Drive and the PRND4 fluid circuits.

The PCM energizes the normally open 1-2 shift solenoid valve, which blocks the 1-2 signal fluid from exhausting. The 1-2 signal fluid pressure is routed to both the 1-2 and the 3-4 shift valves.

The 1-2 signal fluid pressure does not affect the 1-2 shift valve. A combination of spring force and the 2-3 signal fluid pressure keeps the 1-2 shift valve in the upshifted position.

The 1-2 signal fluid pressure moves the valve against a spring force and into the Fourth gear position. The 3-4 drive fluid is routed into the fourth band fluid circuit.

Intermediate and Fourth Servo

The 1-2 signal fluid pressure moves the valve against a spring force and into the Fourth gear position. The 3-4 drive fluid is routed into the fourth band fluid circuit.

3-4 Accumulator

The fourth band fluid is also routed to the 3-4 accumulator piston. Fourth band fluid pressure moves the piston against a combination of spring force and 3-4 accumulator feed fluid pressure. This action absorbs initial fourth band fluid pressure in order to cushion the intermediate and Fourth band apply. The movement of the 3-4 accumulator piston forces some fluid out of the accumulator.

3-4 Accumulator Valve

The 3-4 accumulator feed fluid which is forced from the 3-4 accumulator unseats the #7 checkball and the fluid is routed back to the 3-4 accumulator valve. This pressure forces the 1-2/3-4 accumulator valve against a combination of spring force and torque signal fluid pressure in order to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the intermediate and fourth band apply.

TCC Control Solenoid Valve

When conditions are appropriate, the PCM energized the TCC control solenoid valve in order to initiate the TCC apply. The solenoid valve is pulse width modulated (PWM) in order to provide a smooth TCC apply (Refer to the electrical controls section for a detailed description of the TCC control solenoid valve operation). When energized, the solenoid valve modulates the filtered 2-3 drive fluid into the TCC signal fluid circuit.

TCC Signal fluid pressure modulates the valve against a combination of spring force and TCC regulated apply fluid pressure. This action directs line pressure into the TCC regulated apply fluid circuit in relation to vehicle operating conditions.

Modulated TCC signal fluid pressure moves the valve against a spring force in relation to vehicle operating conditions. This action regulates TCC regulated apply fluid into the apply fluid circuit. At the same time, the release fluid circuit is opened to an orificed exhaust. In this position the valve directs TCC feed limit fluid in order to feed the cooler fluid circuit.

Apply fluid is routed to the torque converter at the same time that release fluid exhausts from the converter. Apply fluid pressure applies the TCC.

Release fluid also exhausts from the TFP Val. Position Sw. Assembly, which signals to the PCM that the TCC is released.

Scheme 190

Overdrive Range, Fourth Gear - Torque Converter Clutch Applied (With Electronic Range Select Mode)

When operating conditions are appropriate, the PCM energizes the 1-2 shift solenoid valve in order to shift the transmission into Fourth gear. In addition, the TCC is applied in Fourth gear. The manual valve remains in the Overdrive position and line pressure continues to feed the Drive and the PRND4 fluid circuits.

The PCM energizes the normally open 1-2 shift solenoid valve, which blocks the 1-2 signal fluid from exhausting. The 1-2 signal fluid pressure is routed to both the 1-2 and the 3-4 shift valves.

The 1-2 signal fluid pressure does not affect the 1-2 shift valve. A combination of spring force and the 2-3 signal fluid pressure keeps the 1-2 shift valve in the upshifted position.

The 1-2 signal fluid pressure moves the valve against a spring force and into the Fourth gear position. The 3-4 drive fluid is routed into the fourth band fluid circuit.

The 1-2 signal fluid pressure moves the valve against a spring force and into the Fourth gear position. The 3-4 drive fluid is routed into the fourth band fluid circuit.

The fourth band fluid is also routed to the 3-4 accumulator piston. Fourth band fluid pressure moves the piston against a combination of spring force and 3-4 accumulator feed fluid pressure. This action absorbs initial fourth band fluid pressure in order to cushion the intermediate and Fourth band apply. The movement of the 3-4 accumulator piston forces some fluid out of the accumulator.

The 3-4 accumulator feed fluid which is forced from the 3-4 accumulator unseats the #7 checkball and the fluid is routed back to the 3-4 accumulator valve. This pressure forces the 1-2/3-4 accumulator valve against a combination of spring force and torque signal fluid pressure in order to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the intermediate and fourth band apply.

When conditions are appropriate, the PCM energized the TCC control solenoid valve in order to initiate the TCC apply. The solenoid valve is pulse width modulated (PWM) in order to provide a smooth TCC apply (Refer to the electrical controls section for a detailed description of the TCC control solenoid valve operation). When energized, the solenoid valve modulates the filtered 2-3 drive fluid into the TCC signal fluid circuit.

TCC Signal fluid pressure modulates the valve against a combination of spring force and TCC regulated apply fluid pressure. This action directs line pressure into the TCC regulated apply fluid circuit in relation to vehicle operating conditions.

Modulated TCC signal fluid pressure moves the valve against a spring force in relation to vehicle operating conditions. This action regulates TCC regulated apply fluid into the apply fluid circuit. At the same time, the release fluid circuit is opened to an orificed exhaust. In this position the valve directs TCC feed limit fluid in order to feed the cooler fluid circuit.

Apply fluid is routed to the torque converter at the same time that release fluid exhausts from the converter. Apply fluid pressure applies the TCC.

Release fluid also exhausts from the TFP Val. Position Sw. Assembly, which signals to the PCM that the TCC is released.

Scheme 191

Overdrive Range, Fourth Gear - Torque Converter Clutch Applied (L4 Hybrid)

When operating conditions are appropriate, the PCM energizes the 1-2 shift solenoid valve in order to shift the transmission into Fourth gear. In addition, the TCC is applied in Fourth gear. The manual valve remains in the Overdrive position and line pressure continues to feed the Drive and the PRND4 fluid circuits.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

The PCM energizes the normally open 1-2 shift solenoid valve, which blocks the 1-2 signal fluid from exhausting. The 1-2 signal fluid pressure is routed to both the 1-2 and the 3-4 shift valves.

The 1-2 signal fluid pressure does not affect the 1-2 shift valve. A combination of spring force and the 2-3 signal fluid pressure keeps the 1-2 shift valve in the upshifted position.

The 1-2 signal fluid pressure moves the valve against a spring force and into the Fourth gear position. The 3-4 drive fluid is routed into the fourth band fluid circuit.

The 1-2 signal fluid pressure moves the valve against a spring force and into the Fourth gear position. The 3-4 drive fluid is routed into the fourth band fluid circuit.

The fourth band fluid is also routed to the 3-4 accumulator piston. Fourth band fluid pressure moves the piston against a combination of spring force and 3-4 accumulator feed fluid pressure. This action absorbs initial fourth band fluid pressure in order to cushion the intermediate and Fourth band apply. The movement of the 3-4 accumulator piston forces some fluid out of the accumulator.

The 3-4 accumulator feed fluid which is forced from the 3-4 accumulator unseats the #7 checkball and the fluid is routed back to the 3-4 accumulator valve. This pressure forces the 1-2/3-4 accumulator valve against a combination of spring force and torque signal fluid pressure in order to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the intermediate and fourth band apply.

When conditions are appropriate, the PCM energized the TCC control solenoid valve in order to initiate the TCC apply. The solenoid valve is pulse width modulated (PWM) in order to provide a smooth TCC apply. When energized, the solenoid valve modulates the filtered 2-3 drive fluid into the TCC signal fluid circuit.

TCC Signal fluid pressure modulates the valve against a combination of spring force and TCC regulated apply fluid pressure. This action directs line pressure into the TCC regulated apply fluid circuit in relation to vehicle operating conditions.

Modulated TCC signal fluid pressure moves the valve against a spring force in relation to vehicle operating conditions. This action regulates TCC regulated apply fluid into the apply fluid circuit. At the same time, the release fluid circuit is opened to an orificed exhaust. In this position the valve directs TCC feed limit fluid in order to feed the cooler fluid circuit.

Apply fluid is routed to the torque converter at the same time that release fluid exhausts from the converter. Apply fluid pressure applies the TCC.

Release fluid also exhausts from the TFP Val. Position Sw. Assembly, which signals to the PCM that the TCC is released.

Scheme 192

Overdrive Range, 4-3 Downshift - Torque Converter Clutch Not Applied (W/O Electronic Range Select Mode)

When the transmission is operating in Overdrive Range - Fourth Gear, a forced 4-3 downshift will occur following a significant increase in throttle position. At minimum throttle, vehicle speed will decrease gradually (coastdown) and the PCM will command a 4-3 downshift. The PCM will also initiate a 4-3 downshift if the engine load is increased while the throttle position remains the same (for example, driving up a steep hill).

During the downshift, except for a coastdown, the PCM senses the increase in the throttle position or the engine load. When this occurs the PCM increases the PCS duty cycle. The increase in duty cycle increases the output fluid pressure from the PCS, thereby increasing the torque signal fluid pressure at the torque signal regulator valve.

Increased torque signal fluid pressure acting on the boost valve increases line pressure at the pressure regulator valve.

The PCM de-energizes the normally open solenoid valve and the 1-2 signal fluid exhausts.

The 1-2 signal fluid pressure exhausts from the 3-4 shift valve and a spring force moves the valve into the Third gear position. This opens the Fourth band fluid circuit to an orificed exhaust in order to help control the band release.

Fourth band fluid exhausts from the servo and a spring force moves the servo to the release position, thereby releasing the band.

The fourth band fluid exhausts from the accumulator. A combination of spring force and 3-4 accumulator feed fluid pressure moves the accumulator piston to the Third gear position.

1-2/3-4 Accumulator Valve

The accumulator valve regulates line pressure into the 1-2/3-4 accumulator fluid circuit in order to fill the 3-4 accumulator. Torque signal fluid pressure controls this regulation. Increased torque signal fluid pressure regulates accumulator fluid to a higher pressure.

The PCM commands TCC release prior to initiating a 4-3 downshift. When the TCC is in the release position, release fluid pressure is routed to the pressure switch assembly. This fluid pressure signals the PCM that the TCC is in the release position. The TCC is not applied under normal operating conditions in Third gear.

Scheme 193

Drive Range, Manual Third (from Overdrive Range) (W/O Electronic Range Select Mode)

Note. The operating states for the shift solenoids follow the normal operation depending on vehicle driving conditions

A manual 4-3 downshift is accomplished by moving the gear selector lever to the Manual Third (3) position. In Manual Third the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the coast clutch is applied in all manual ranges in order to provide engine compressing braking whenever appropriated. The following information explains the additional changes during a Manual 4-3 downshift as compared to a forced 4-3 downshift. Refer to Overdrive Range, 4-3 Downshift - Torque Converter Clutch Not Applied (W/O Electronic Range Select Mode) for a complete description of a 4-3 downshift.

The manual valve moves into the Manual Third (3) position and line pressure enters the D321 fluid circuit. Also the manual valve blocks line pressure from the PRND4 fluid circuit and the PRND4 fluid exhausts past the manual valve.

D321 fluid pressure assists a spring force in order to keep the valve in the Third gear position under any conditions. this opens the Forth band fluid circuit to an orificed exhaust and the Intermediate and Fourth band releases, thereby preventing Fourth gear.

PRND4 fluid exhausts from the TFP Val. Position Sw. Assembly, which signals to the PCM that the manual valve is in the Manual Third position.

Manual Third - Second and First Gears

The transmission operates the same in Manual Third as in Overdrive range with the exception that Fourth gear is prevented. The transmission will upshift and downshift between First, Second, and Third gears as in Overdrive range. However, engine compression braking is not available in Manual Third - First and Second gears, and the vehicle will coast when you release the throttle.

Scheme 194

Manual Third Gear (With Electronic Range Select Mode)

Note. The operating states for the shift solenoids follow the normal operation depending on vehicle driving conditions

A manual 4-3 downshift is accomplished by moving the gear selector lever to the Manual Third (3) position. In Manual Third the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the coast clutch is applied in all manual ranges in order to provide engine compressing braking whenever appropriated. The following information explains the additional changes during a Manual 4-3 downshift as compared to a forced 4-3 downshift. Refer to Overdrive Range, 4-3 Downshift - Torque Converter Clutch Not Applied (W/O Electronic Range Select Mode) for a complete description of a 4-3 downshift.

The manual valve moves into the Manual Third (3) position and line pressure enters the D321 fluid circuit. Also the manual valve blocks line pressure from the PRND4 fluid circuit and the PRND4 fluid exhausts past the manual valve.

D321 fluid pressure assists a spring force in order to keep the valve in the Third gear position under any conditions. this opens the Forth band fluid circuit to an orificed exhaust and the Intermediate and Fourth band releases, thereby preventing Fourth gear.

PRND4 fluid exhausts from the TFP Val. Position Sw. Assembly, which signals to the PCM that the manual valve is in the Manual Third position.

The transmission operates the same in Manual Third as in Overdrive range with the exception that Fourth gear is prevented. The transmission will upshift and downshift between First, Second, and Third gears as in Overdrive range. However, engine compression braking is not available in Manual Third - First and Second gears, and the vehicle will coast when you release the throttle.

Scheme 195

Manual Third Gear (L4 Hybrid)

Note. The operating states for the shift solenoids follow the normal operation depending on vehicle driving conditions.

A manual 4-3 downshift is accomplished by moving the gear selector lever to the Manual Third (3) position. In Manual Third the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the coast clutch is applied in all manual ranges in order to provide engine compressing braking whenever appropriated.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

The manual valve moves into the Manual Third (3) position and line pressure enters the D321 fluid circuit. Also the manual valve blocks line pressure from the PRND4 fluid circuit and the PRND4 fluid exhausts past the manual valve.

D321 fluid pressure assists a spring force in order to keep the valve in the Third gear position under any conditions. this opens the Forth band fluid circuit to an orificed exhaust and the Intermediate and Fourth band releases, thereby preventing Fourth gear.

PRND4 fluid exhausts from the TFP Val. Position Sw. Assembly, which signals to the PCM that the manual valve is in the Manual Third position.

The transmission operates the same in Manual Third as in Overdrive range with the exception that Fourth gear is prevented. The transmission will upshift and downshift between First, Second, and Third gears as in Overdrive range. However, engine compression braking is not available in Manual Third - First and Second gears, and the vehicle will coast when you release the throttle.

Scheme 196

Drive Range, Manual Second (from Drive, Manual Third) (W/O Electronic Range Select Mode)

A manual 3-2 downshift is initiated by moving the gear selector lever to the Manual Second (2) position. However, the transmission will not downshift into Second gear until vehicle speed is below approximately 99 km/h (62 mph). At higher vehicle speeds the PCM will keep the 2-3 shift solenoid energized (On) and the transmission will operate in Manual Second - Third Gear as a safety precaution. In Manual Second the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the coast clutch remains applied as in Manual Third, and the clutch provides engine compression braking in the Third and the Second gears. The transmission upshifts and downshifts between First and Second gears as in Overdrive gear.

Line pressure is routed into the D21 fluid circuit when the selector lever is moved into the Manual Second (2) position. Line pressure continues to feed the D321 fluid circuit as in Manual Third.

The PCM de-energized the 2-3 shift solenoid valve when the vehicle operating conditions are appropriate for a 3-2 downshift. With the solenoid valve Off, a 2-3 signal fluid exhausts through the 2-3 shift solenoid valve.

A spring force moves the 2-3 shift valve into the Second gear position when the 2-3 signal fluid exhausts. The D21 fluid continues through the valve and the fluid is also routed into the intermediate band feed fluid circuit. The 3-4 drive fluid, which feeds the direct clutch, exhausts past the 2-3 shift valve.

The direct clutch fluid exhausts and the direct clutch releases.

#6 Checkball (Direct Clutch Release)

Exhausting direct clutch fluid seats the #6 checkball. This fluid is forced through the #25 orifice in order to help to control the direct clutch release.

Direct clutch feed fluid exhausts from the 2-3 accumulator, unseats the #5 checkball, and exhausts past the 2-3 shift valve. The 2-3 accumulator feed fluid fills the 2-3 accumulator as the direct clutch feed fluid exhausts.

The 1-2 shift solenoid valve is Off when the PCM commands the Second gear. A spring force holds the 1-2 shift valve in the upshifted position. Intermediate band feed fluid is routed through the valve and into the intermediate band fluid circuit.

#3 Checkball (Intermediate Band Apply)

Intermediate band fluid pressure seats the #3 checkball and is forced through the #8 orifice. This orifice helps to control the intermediate band apply.

Intermediate band fluid pressure is routed to the inner area of the intermediate and Fourth servo piston. This fluid pressure moves the servo piston and apply pin in order to apply the intermediate and Fourth band. The band provides engine compression braking in Manual Second - Second Gear.

The D21 fluid from the 2-3 shift valve is routed to the TFP Val. Position Sw. assembly, which signals to the PCM that the manual valve is in the Manual Second position.

Pressure Control Solenoid Valve

The PCM increases the PCS duty cycle in order to increase the operating range of torque signal fluid pressure in Manual Second. This provides increased line pressure for the additional torque requirements during engine compression braking and increased engine load in Manual Second.

The PCM will release the TCC before downshifting into Manual Second. The TCC will not reapply in Second gear under normal operating conditions.

Scheme 197

Manual Second Gear (With Electronic Range Select Mode)

A manual 3-2 downshift is initiated by moving the gear selector lever to the Manual Second (2) position. However, the transmission will not downshift into Second gear until vehicle speed is below approximately 99 km/h (62 mph). At higher vehicle speeds the PCM will keep the 2-3 shift solenoid energized (On) and the transmission will operate in Manual Second - Third Gear as a safety precaution. In Manual Second the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the coast clutch remains applied as in Manual Third, and the clutch provides engine compression braking in the Third and the Second gears. The transmission upshifts and downshifts between First and Second gears as in Overdrive gear.

Line pressure is routed into the D21 fluid circuit when the selector lever is moved into the Manual Second (2) position. Line pressure continues to feed the D321 fluid circuit as in Manual Third.

The PCM de-energized the 2-3 shift solenoid valve when the vehicle operating conditions are appropriate for a 3-2 downshift. With the solenoid valve Off, a 2-3 signal fluid exhausts through the 2-3 shift solenoid valve.

A spring force moves the 2-3 shift valve into the Second gear position when the 2-3 signal fluid exhausts. The D21 fluid continues through the valve and the fluid is also routed into the intermediate band feed fluid circuit. The 3-4 drive fluid, which feeds the direct clutch, exhausts past the 2-3 shift valve.

The direct clutch fluid exhausts and the direct clutch releases.

Exhausting direct clutch fluid seats the #6 checkball. This fluid is forced through the #25 orifice in order to help to control the direct clutch release.

Direct clutch feed fluid exhausts from the 2-3 accumulator, unseats the #5 checkball, and exhausts past the 2-3 shift valve. The 2-3 accumulator feed fluid fills the 2-3 accumulator as the direct clutch feed fluid exhausts.

The 1-2 shift solenoid valve is Off when the PCM commands the Second gear. A spring force holds the 1-2 shift valve in the upshifted position. Intermediate band feed fluid is routed through the valve and into the intermediate band fluid circuit.

Intermediate band fluid pressure seats the #3 checkball and is forced through the #8 orifice. This orifice helps to control the intermediate band apply.

Intermediate band fluid pressure is routed to the inner area of the intermediate and Fourth servo piston. This fluid pressure moves the servo piston and apply pin in order to apply the intermediate and Fourth band. The band provides engine compression braking in Manual Second - Second Gear.

The D21 fluid from the 2-3 shift valve is routed to the TFP Val. Position Sw. assembly, which signals to the PCM that the manual valve is in the Manual Second position.

The PCM increases the PCS duty cycle in order to increase the operating range of torque signal fluid pressure in Manual Second. This provides increased line pressure for the additional torque requirements during engine compression braking and increased engine load in Manual Second.

The PCM will release the TCC before downshifting into Manual Second. The TCC will not reapply in Second gear under normal operating conditions.

Scheme 198

Manual Second Gear (L4 Hybrid)

A manual 3-2 downshift is initiated by moving the gear selector lever to the Manual Second (2) position. However, the transmission will not downshift into Second gear until vehicle speed is below approximately 99 km/h (62 mph). At higher vehicle speeds the PCM will keep the 2-3 shift solenoid energized (On) and the transmission will operate in Manual Second - Third Gear as a safety precaution. In Manual Second the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the coast clutch remains applied as in Manual Third, and the clutch provides engine compression braking in the Third and the Second gears. The transmission upshifts and downshifts between First and Second gears as in Overdrive gear.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

Line pressure is routed into the D21 fluid circuit when the selector lever is moved into the Manual Second (2) position. Line pressure continues to feed the D321 fluid circuit as in Manual Third.

The PCM de-energized the 2-3 shift solenoid valve when the vehicle operating conditions are appropriate for a 3-2 downshift. With the solenoid valve Off, a 2-3 signal fluid exhausts through the 2-3 shift solenoid valve.

A spring force moves the 2-3 shift valve into the Second gear position when the 2-3 signal fluid exhausts. The D21 fluid continues through the valve and the fluid is also routed into the intermediate band feed fluid circuit. The 3-4 drive fluid, which feeds the direct clutch, exhausts past the 2-3 shift valve.

The direct clutch fluid exhausts and the direct clutch releases.

Exhausting direct clutch fluid seats the #6 checkball. This fluid is forced through the #25 orifice in order to help to control the direct clutch release.

Direct clutch feed fluid exhausts from the 2-3 accumulator, unseats the #5 checkball, and exhausts past the 2-3 shift valve. The 2-3 accumulator feed fluid fills the 2-3 accumulator as the direct clutch feed fluid exhausts.

The 1-2 shift solenoid valve is Off when the PCM commands the Second gear. A spring force holds the 1-2 shift valve in the upshifted position. Intermediate band feed fluid is routed through the valve and into the intermediate band fluid circuit.

Intermediate band fluid pressure seats the #3 checkball and is forced through the #8 orifice. This orifice helps to control the intermediate band apply.

Intermediate band fluid pressure is routed to the inner area of the intermediate and Fourth servo piston. This fluid pressure moves the servo piston and apply pin in order to apply the intermediate and Fourth band. The band provides engine compression braking in Manual Second - Second Gear.

The D21 fluid from the 2-3 shift valve is routed to the TFP Val. Position Sw. assembly, which signals to the PCM that the manual valve is in the Manual Second position.

The PCM increases the PCS duty cycle in order to increase the operating range of torque signal fluid pressure in Manual Second. This provides increased line pressure for the additional torque requirements during engine compression braking and increased engine load in Manual Second.

The PCM will release the TCC before downshifting into Manual Second. The TCC will not reapply in Second gear under normal operating conditions.

Scheme 199

Drive Range, Manual First (from Drive, Manual Second) (W/O Electronic Range Select Mode)

Note. As a safety feature, Manual First - Third Gear is also possible at high speeds.

A manual 2-1 downshift is initiated by moving the gear selector lever to the Manual First (1) position. However, the transmission will not downshift into First gear until the vehicle speed is below approximately 60 km/h (37 mph). At higher vehicle speeds the PCM will keep the 1-2 shift solenoid valve de-energized (Off) and the transmission will operate in Manual First - Second Gear. In Manual First the transmission is electronically prevented from upshifting into Third or Fourth gears under any conditions. Also, the coast clutch remains applied, as in Manual Third and Manual Second, and the clutch provides engine compression braking in First and Second gears.

Line pressure is routed into the Low fluid circuit when the selector lever is moved into the Manual First (1) position. Line pressure continues to feed the Drive, the D321, and the D21 fluid circuits as in Manual Second.

Low fluid pressure is routed to the TFP Val. Position Sw. Assembly, which signals to the PCM that the manual valve is in the Manual First position.

#1 Checkball (Low/PRN)

Low fluid pressure seats the #1 checkball against the PRN fluid circuit and this pressure fills the Low/PRN fluid circuit. Low/PRN fluid is routed to the 1-2 shift valve.

The PCM energizes the 1-2 shift solenoid valve when vehicle speed is below approximately 48-56 km/h (30-35 mph). The 1-2 signal fluid is blocked from exhausting through the solenoid valve.

The 1-2 signal fluid pressure shifts the valve into the downshifted position against a spring force, and the following changes occur

1. The 2-3 drive fluid circuit is open to an exhaust past the valve
2. The intermediate band fluid is exhausted past the valve
3. the Lo/PRN fluid is routed into the low band fluid circuit

The Second clutch fluid exhausts from the clutch piston and through the 2-3 drive fluid circuit. This releases the Second clutch, and the transmission operates in First gear.

Second clutch feed fluid exhausts from the 1-2 accumulator, and the fluid exhausts past the #2 checkball and through the 2-3 drive fluid circuit. The 1-2 accumulator feed fluid fills the 1-2 accumulator as the second clutch fluid exhausts.

The accumulator valve regulates the line pressure into the 1-2/3-4 accumulator fluid circuit in order to fill the 1-2 accumulator. Torque signal fluid pressure controls this regulation. Accumulator fluid pressure is regulated to a higher pressure with greater torque signal fluid pressure.

Filtered 2-3 drive fluid exhausts from the solenoid and through the 2-3 drive fluid circuit.

Intermediate band fluid exhausts from the servo piston. A spring force moves the piston and the apply pin, and the intermediate and fourth band releases. However, the intermediate and fourth band remains applied in Manual First - Second Gear in order to achieve engine compression braking.

Low band fluid pressure is routed to the inner area of the Low and Reverse servo in order to apply the Low and Reverse band. The Low and Reverse band provides engine compression braking when the throttle is released in Manual First - First Gear.

Scheme 200

Manual First Gear (With Electronic Range Select Mode)

Note. As a safety feature, Manual First - Third Gear is also possible at high speeds.

A manual 2-1 downshift is initiated by moving the gear selector lever to the Manual First (1) position. However, the transmission will not downshift into First gear until the vehicle speed is below approximately 60 km/h (37 mph). At higher vehicle speeds the PCM will keep the 1-2 shift solenoid valve de-energized (Off) and the transmission will operate in Manual First - Second Gear. In Manual First the transmission is electronically prevented from upshifting into Third or Fourth gears under any conditions. Also, the coast clutch remains applied, as in Manual Third and Manual Second, and the clutch provides engine compression braking in First and Second gears.

Line pressure is routed into the Low fluid circuit when the selector lever is moved into the Manual First (1) position. Line pressure continues to feed the Drive, the D321, and the D21 fluid circuits as in Manual Second.

Low fluid pressure is routed to the TFP Val. Position Sw. Assembly, which signals to the PCM that the manual valve is in the Manual First position.

Low fluid pressure seats the #1 checkball against the PRN fluid circuit and this pressure fills the Low/PRN fluid circuit. Low/PRN fluid is routed to the 1-2 shift valve.

The PCM energizes the 1-2 shift solenoid valve when vehicle speed is below approximately 48-56 km/h (30-35 mph). The 1-2 signal fluid is blocked from exhausting through the solenoid valve.

The 1-2 signal fluid pressure shifts the valve into the downshifted position against a spring force, and the following changes occur

1. The 2-3 drive fluid circuit is open to an exhaust past the valve
2. The intermediate band fluid is exhausted past the valve
3. the Lo/PRN fluid is routed into the low band fluid circuit

The Second clutch fluid exhausts from the clutch piston and through the 2-3 drive fluid circuit. This releases the Second clutch, and the transmission operates in First gear.

Second clutch feed fluid exhausts from the 1-2 accumulator, and the fluid exhausts past the #2 checkball and through the 2-3 drive fluid circuit. The 1-2 accumulator feed fluid fills the 1-2 accumulator as the second clutch fluid exhausts.

The accumulator valve regulates the line pressure into the 1-2/3-4 accumulator fluid circuit in order to fill the 1-2 accumulator. Torque signal fluid pressure controls this regulation. Accumulator fluid pressure is regulated to a higher pressure with greater torque signal fluid pressure.

Filtered 2-3 drive fluid exhausts from the solenoid and through the 2-3 drive fluid circuit.

Intermediate band fluid exhausts from the servo piston. A spring force moves the piston and the apply pin, and the intermediate and fourth band releases. However, the intermediate and fourth band remains applied in Manual First - Second Gear in order to achieve engine compression braking.

Low band fluid pressure is routed to the inner area of the Low and Reverse servo in order to apply the Low and Reverse band. The Low and Reverse band provides engine compression braking when the throttle is released in Manual First - First Gear. The low band fluid is routed to the 3-4 shift valve. The pressure moves the 3-4 shift valve against the 1-2 signal fluid.

Scheme 201

Manual First Gear (L4 Hybrid)

Note. As a safety feature, Manual First - Third Gear is also possible at high speeds.

A manual 2-1 downshift is initiated by moving the gear selector lever to the Manual First (1) position. However, the transmission will not downshift into First gear until the vehicle speed is below approximately 60 km/h (37 mph). At higher vehicle speeds the PCM will keep the 1-2 shift solenoid valve de-energized (Off) and the transmission will operate in Manual First - Second Gear. In Manual First the transmission is electronically prevented from upshifting into Third or Fourth gears under any conditions. Also, the coast clutch remains applied, as in Manual Third and Manual Second, and the clutch provides engine compression braking in First and Second gears.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

Line pressure is routed into the Low fluid circuit when the selector lever is moved into the Manual First (1) position. Line pressure continues to feed the Drive, the D321, and the D21 fluid circuits as in Manual Second.

Low fluid pressure is routed to the TFP Val. Position Sw. Assembly, which signals to the PCM that the manual valve is in the Manual First position.

Low fluid pressure seats the #1 checkball against the PRN fluid circuit and this pressure fills the Low/PRN fluid circuit. Low/PRN fluid is routed to the 1-2 shift valve.

The PCM energizes the 1-2 shift solenoid valve when vehicle speed is below approximately 48-56 km/h (30-35 mph). The 1-2 signal fluid is blocked from exhausting through the solenoid valve.

The 1-2 signal fluid pressure shifts the valve into the downshifted position against a spring force, and the following changes occur

1. The 2-3 drive fluid circuit is open to an exhaust past the valve
2. The intermediate band fluid is exhausted past the valve
3. the Lo/PRN fluid is routed into the low band fluid circuit

The Second clutch fluid exhausts from the clutch piston and through the 2-3 drive fluid circuit. This releases the Second clutch, and the transmission operates in First gear.

Second clutch feed fluid exhausts from the 1-2 accumulator, and the fluid exhausts past the #2 checkball and through the 2-3 drive fluid circuit. The 1-2 accumulator feed fluid fills the 1-2 accumulator as the second clutch fluid exhausts.

The accumulator valve regulates the line pressure into the 1-2/3-4 accumulator fluid circuit in order to fill the 1-2 accumulator. Torque signal fluid pressure controls this regulation. Accumulator fluid pressure is regulated to a higher pressure with greater torque signal fluid pressure.

Filtered 2-3 drive fluid exhausts from the solenoid and through the 2-3 drive fluid circuit.

Intermediate band fluid exhausts from the servo piston. A spring force moves the piston and the apply pin, and the intermediate and fourth band releases. However, the intermediate and fourth band remains applied in Manual First - Second Gear in order to achieve engine compression braking.

Low band fluid pressure is routed to the inner area of the Low and Reverse servo in order to apply the Low and Reverse band. The Low and Reverse band provides engine compression braking when the throttle is released in Manual First - First Gear. The low band fluid is routed to the 3-4 shift valve. The pressure moves the 3-4 shift valve against the 1-2 signal fluid.

Scheme 202

Scheme 203

Scheme 204

Scheme 205

Scheme 206

Scheme 207

Scheme 208

Scheme 209

Scheme 210

Scheme 211

Scheme 212

See also:
• Transmission Fluid Temperature Sensor Specifications
• Transmission Range Switch Logic
• TAP Shift Operation
• Electronic Component Description
• Reverse (W/O Electronic Range Select Mode)
• Reverse (With Electronic Range Select Mode)
• Reverse (L4 Hybrid)
• Overdrive Range, 4-3 Downshift - Torque Converter Clutch Not Applied (W/O Electronic Range Select Mode)