System Operation
The PCM and its input/output network controls the following operations:
Shift timing
Line pressure (shift feel)
The transmission control strategy is separate from the engine control strategy in the PCM, although some of the input signals are shared. When determining the best operating strategy for transmission operation, the PCM uses input information from engine and driver related sensors and switches.
In addition, the PCM receives input signals from transmission related sensors and switches. The PCM uses these signals when determining transmission operating strategy.
Using all of these input signals, the PCM can determine when the time and conditions are right for a shift or when to apply or release the TCC. It also determines the best line pressure to optimize shift engagement feel. To accomplish this, the PCM uses output solenoids to control transmission operation.
The transmission control strategy is separate from the engine control strategy in the PCM, although some of the input signals are shared. When determining the best operating strategy for transmission operation, the PCM uses input information from engine and driver related sensors and switches. In addition, the PCM receives input signals from transmission related sensors and switches. The PCM uses these signals when determining transmission operating strategy. Using all of these input signals, the PCM can determine when the time and conditions are right for a shift or when to apply or release the TCC. It also determines the best line pressure to optimize shift engagement feel. To accomplish this, the PCM uses output solenoids to control transmission operation.
Component Description
Hydraulic System Diagram
Hydraulic Circuit Identification Chart
| Circuit Name | Description |
|---|---|
| BREVA | BREV5 pressure from the drive enable valve to the clutch A regulator valve. |
| BREV5 | BREV 5F pressure from the clutch A latch valve to the drive enable valve and the No. 2 shuttle ball. |
| BREV 5F | Regulated line pressure from the CL B circuit directed to the A clutch latch valve by the B clutch latch valve. |
| BREV5/SS1 | BREV5 or SS1 pressure from the No. 2 shuttle ball to the solenoid multiplex valve. |
| CAPLY | Apply circuit to the torque converter, also the return circuit during TCC release. |
| CAPLY EX | TCC releases pressure from the bypass clutch control regulator valve to the converter release regulator valve. |
| CAPLY F | Line pressure from the PUMP circuit directed to the bypass clutch control regulator valve by the main regulator valve. |
| CL A | Regulated line pressure from the clutch A regulator valve to the clutch A latch valve and the forward (A) clutch to apply the clutch. |
| CLA FB | Regulated line pressure from the clutch A latch valve that feeds back to the clutch A regulator valve. |
| CL B | Regulated line pressure from the clutch B regulator valve to the clutch B latch valve and the direct (B) clutch to apply the clutch. |
| CLB FB | Regulated line pressure from the clutch B latch valve that feeds back to the clutch B regulator valve. |
| CL C | Regulated line pressure from the clutch C regulator valve to the intermediate (C) clutch to apply the clutch. |
| CL D1 | Regulated line pressure from the clutch D1 regulator valve to the clutch D1 latch valve and the low/reverse (D) clutch to apply the clutch. |
| CL D1 FB | Regulated line pressure from the clutch D1 latch valve that feeds back to the clutch D1 regulator valve. |
| CL D2 | Regulated line pressure from the clutch D2 regulator valve to the low/reverse (D) clutch to apply the clutch. |
| CL DC | Regulated solenoid output pressure from SSD directed by the solenoid multiplex valve to the D1 and D2 regulator and latch valves to apply the low/reverse (D) clutch. |
| CLE | Regulated line pressure from the clutch E regulator valve to the clutch E latch valve and the Overdrive (O/D) (E) clutch to apply the clutch. |
| CLEC | Regulated solenoid output pressure from the CLEC F circuit directed by the drive enable valve to the clutch E regulator and latch valves to apply the clutch. |
| CLEC F | Regulated solenoid output pressure from the VFS4 circuit directed to the drive enable valve by the solenoid multiplex valve to move the clutch E regulator and latch valves to apply the O/D (E) clutch. |
| CLE FB | Regulated line pressure from the clutch E latch valve that feeds back to the clutch E regulator valve. |
| CL EXH | Line pressure regulated to approximately 21 kPa (3 psi) by the D2 latch valve that supplies exhaust pressure to the A, B, C, D1 and E clutch when the clutches are released. |
| COOLF | Pressure from the lubrication control valve to the oil cooler or the thermal bypass valve that feeds the lubrication circuit. |
| CREL | Pressure supplied to the torque converter by the converter release regulator valve to release the TCC. |
| CREL F | Line pressure from the main regulator valve that supplies the converter release regulator valve and the lubrication control valve. |
| DBACK | CAPLY EX pressure directed to the drain back valve by the converter release regulator valve. |
| DRIVE | Line pressure directed by the manual valve to the A, C and E clutch regulator valves and the No. 1 shuttle ball. |
| LUBE | Transmission lubrication circuit supplied by the COOLF circuit after the fluid circulates the transmission fluid cooler or is returned by the cooler bypass valve. |
| PUMP | Line pressure supplied by the pump to the manual valve, solenoid pressure regulator valve, main regulator valve, clutch D1 regulator valve, clutch D2 regulator valve and clutch D2 latch valve. |
| REV | Line pressure from the manual valve to the No. 1 shuttle ball and the solenoid multiplex valve. |
| REV/DRIVE | REV or DRIVE pressure from the No. 1 shuttle ball to the clutch B regulator valve. |
| SCHG | Line pressure from the main regulator valve to the pump suction port. |
| SREG | Line pressure from the solenoid regulator valve that supplies pressure to the 7 solenoids, SSA, SSB, SSC, SSD, SSE, TCC solenoid and LPC solenoid. |
| SS1 | Solenoid output pressure from SSE to the drive enable valve and to shuttle ball No. 2 to direct SSD output pressure to clutch E regulator and latch valves to apply the O/D (E) clutch. |
| VFS1 | Solenoid output pressure from SSA to the A clutch regulator and latch valve to apply the forward (A) clutch. |
| VFS2 | Solenoid output pressure from SSB to the B clutch regulator and latch valve to apply the direct (B) clutch and is also routed to the D1 latch valve. |
| VFS2D | SSB output pressure from the VFS2 circuit directed to the clutch B regulator valve by the D1 latch valve. |
| VFS3 | Solenoid output pressure from SSC to the C clutch regulator valve to apply the intermediate (C) clutch and is also routed to the clutch E latch valve. |
| VFS3E | SSC output pressure from the VFS3 circuit directed to the clutch C regulator valve by the clutch E latch valve. |
| VFS4 | Solenoid output pressure from SSD to the solenoid multiplex valve to apply either the D or E clutch. |
| VFS5 | Solenoid output pressure from the LPC solenoid to the main regulator valve to control line pressure. |
| VFS6 | Solenoid output pressure from the TCC solenoid to the bypass clutch control regulator valve and the converter release regulator valve to control the TCC. |
Valve Body Maps for Solenoid and Line Pressure
Solenoid Body Hydraulic Passages
Upper Valve Body Passages
Separator Plate Passages (Lower Valve Body Side)
Lower Valve Body Passages
Valve Body - To - Transmission Case Hydraulic Passages
Line Pressure Hydraulic Circuits
The PCM controls line pressure with the LPC solenoid. Varying pressure from the LPC solenoid effects shift feel while allowing sufficient pressure for clutch application.
When the engine is running, the pump supplies pressure to the main regulator valve through the PUMP circuit. The position of the main regulator valve controls line pressure (in the PUMP circuit). Pressure from the LPC solenoid through the VFS5 circuit controls the position of the main regulator valve.
The main regulator valve varies pressure in the SCHG circuit. The higher the pressure in the SCHG circuit, the lower the line pressure (PUMP circuit) is. As SCHG pressure decreases, line pressure (PUMP circuit) increases.
Line Pressure Hydraulic Circuits
Lubrication Hydraulic Circuits
The main regulator valve supplies pressure to the lubrication control valve through the CREL F circuit. When the TCC is applied, the lubrication control valve supplies the transmission lubrication through the COOLF circuit to the LUBE circuit.
When the TCC is released, return fluid from the torque converter is supplied to the LUBE circuit through the CAPLY, CAPLY EX and DBACK circuits.
Pressure in the LUBE circuit either circulates through the thermal bypass valve when TFT is below operating temperature or through the transmission fluid cooler when the transmission fluid is at or above operating temperature. Return fluid from the thermal bypass valve or the transmission fluid cooler enters the input shaft through the pump assembly and flows through passages in the input shaft, intermediate shaft and output shaft to provide lubrication for the transmission.
Lubrication Hydraulic Circuits
Transmission Electronic Control System
The PCM control the electronic functions of this transmission. A plastic molded leadframe is bolted to the main control assembly. The leadframe contains the TSS, OSS, TFT and TR sensors.
The PCM receives input signals from engine and transmission sensors and uses these inputs to control line pressure, shift time, TCC, and shift solenoids. The PCM also provides power and ground for the reverse lamp relay coil and provides a PARK/NEUTRAL start enable signal.
The following is a list of direct engine and driver inputs to the PCM along with module information from the vehicle CAN:
- Engine speed
- Engine torque
- ECT
- Engine Oil Temperature (EOT)
- TP
- APP
- BPP
- ABS wheel speed
- Traction Control (ATC) status
The PCM also:
- Monitors inputs and outputs for the presence of faults.
- Stores DTCs related to detected faults.
- Provides outputs on the CAN for TR, OSS, TSS, TFT, current gear and A/C inhibit.
- Provides OBD information using the CAN to illuminate the MIL or TCIL.
- Provides diagnostic information to a scan tool through the DLC.
If the PCM detects a system or component fault, it substitutes a default value or signal using Failure Mode and Effect Management strategies.
The PCM also uses Failure Mode and Effect Management strategies to compensate for electrical or mechanical shift solenoid and apply component faults that result in alternate shift patterns.
If the transmission loses complete electronic control, it operates in a fail-safe mode with:
- Maximum line pressure in all transmission ranges
- Functional PARK, REVERSE and NEUTRAL positions
- Operation in 3rd or 5th gear (depending on the failure conditions) when the selector lever is in the DRIVE, 3, 2 or 1 position
- TCC is released in all transmission ranges and gears
Torque Converter Clutch (TCC) Proportional (VFS)
The TCC solenoid is a VFS that varies hydraulic pressure by actuating a hydraulic valve. The PCM applies variable current to the TCC solenoid which varies pressure in the VFS6 hydraulic circuit to the Converter Release Regulator Valve and the Bypass Clutch Control Regulator Valve. The TCC solenoid uses proportional operation. As the current from the PCM decreases, the pressure from the solenoid decreases. As the current from the PCM increases, the pressure from the solenoid increases. The TCC solenoid is supplied hydraulic pressure from the SREG circuit. With zero current, the TCC solenoid fully closes the hydraulic valve which applies the minimum amount of hydraulic pressure to the Converter Release Regulator Valve and the Bypass Clutch Control Regulator Valve through the VFS6 hydraulic circuit and releases the TCC. With maximum current to the solenoid, the hydraulic valve fully opens the outlet port for maximum pressure to the VFS6 hydraulic circuit to apply the TCC.
| Item | Description |
|---|---|
| 1 | Low Current |
| 2 | Low Exhaust |
| 3 | SREG Circuit Fluid (Supply) |
| 4 | Low Pressure To VFS5 Hydraulic Circuit |
| 5 | High Current |
| 6 | High Exhaust |
| 7 | SREG Circuit Fluid (Supply) |
| 8 | High Pressure To VFS5 Hydraulic Circuit |
Shift Solenoid A (SSA), Shift Solenoid B (SSB), Shift Solenoid C (SSC) and Shift Solenoid D (SSD)
| Item | Description |
|---|---|
| A | Low Current |
| B | High Current |
| 1 | High Exhaust |
| 2 | SREG Circuit Fluid (Supply) |
| 3 | Low Pressure To Clutch Regulator And Latch Valves |
| 4 | Low Exhaust |
| 5 | SREG Circuit Fluid (Supply) |
| 6 | High Pressure To Clutch Regulator And Latch Valves |
| 7 | SSA Variable Force Solenoid (VFS) |
| 8 | SSC VFS |
SSB and SSD use inverse proportional operation. As the current from the PCM decreases, the pressure from the solenoid increases. As the current from the PCM increases, the pressure from the solenoid decreases. SSB and SSD are supplied hydraulic pressure from the SREG circuit.
With zero current, SSB and SSD fully open the hydraulic valves which applies maximum hydraulic pressure to the regulator and latch valves to apply the clutch that it controls. With maximum current to the solenoids, the hydraulic valve fully closes to apply zero amount of hydraulic pressure to the regulator and latch valves of the clutch that it controls and releases the clutch.
Shift solenoids A through D are VFS that vary hydraulic pressure by actuating a hydraulic valve.
The PCM applies variable current to the shift solenoids which varies pressure in the hydraulic circuit to the regulator and latch valves of the clutch that it controls.
SSA and SSC use proportional operation. As the current from the PCM decreases, the pressure from the solenoid decreases. As the current from the PCM increases, the pressure from the solenoid increases. SSA and SSC are supplied hydraulic pressure from the SREG circuit.
With zero current, SSA and SSC fully close the hydraulic valves which applies zero amount of hydraulic pressure to the regulator and latch valves of the clutch that it controls and releases the clutch. With maximum current to the solenoids, the hydraulic valves fully open for maximum pressure to the regulator and latch valves to apply the clutch.
Shift Solenoid B (SSB) and Shift Solenoid D (SSD) Inverse Proportional Variable VFS
| Item | Description |
|---|---|
| A | Low Current |
| B | High Current |
| 1 | Low Exhaust |
| 2 | SREG Circuit Fluid (Supply) |
| 3 | High Pressure To Clutch Regulator And Latch Valves |
| 4 | High Exhaust |
| 5 | SREG Circuit Fluid (Supply) |
| 6 | Low Pressure To Clutch Regulator And Latch Valves |
| 7 | SSB Variable Force Solenoid (VFS) |
| 8 | SSD VFS |
Shift Solenoid E (SSE) ON/OFF Solenoid
| Item | Description |
|---|---|
| A | Off |
| B | On |
| 1 | Exhaust Port Connects To Outlet Port (SS1 Circuit) |
| 2 | SREG Circuit Fluid (Supply) |
| 3 | Outlet Port (SS1 Circuit) |
| 4 | SREG Circuit Fluid (Supply) |
Turbine Shaft Speed (TSS) Sensor
The TSS is a Hall-effect type sensor that provides a signal to the PCM that changes in frequency as the rotating speed of the forward (1, 2, 3, 4) clutch cylinder varies.
The PCM compares the TSS sensor signal with the engine speed information to determine the amount of slip occurring in the torque converter.
The PCM also compares the TSS sensor signal with the OSS sensor signal to determine the gear ratio provided by the rear planetary gearset.
The PCM uses the TSS sensor signal as an input for its strategies for shifts and TCC operation. The PCM also uses the TSS sensor signal for transmission fault detection and diagnostics.
Output Shaft Speed (OSS) Sensor
The OSS sensor is a Hall-effect type sensor that provides a signal to the PCM that changes in frequency as the rotating speed of the output shaft ring gear varies.
The PCM also compares the OSS sensor signal with the TSS sensor signal to determine the gear ratio provided by the rear planetary gearset.
The PCM uses the OSS sensor signal as an input for its strategies for shifts and TCC operation. The PCM also uses the OSS sensor signal for transmission fault detection and diagnostics.
Transmission Fluid Temperature (TFT) Sensor
The TFT sensor is a temperature dependent resistor that is in contact with transmission fluid in the transmission sump area.
The PCM monitors the voltage across the TFT sensor, which changes as transmission fluid temperature varies.
The PCM uses the TFT sensor signal as an input for its strategy for shifting and TCC operation. The PCM also uses the TFT sensor signal for transmission fault detection and diagnostics.
Transmission Range (TR) Sensor
The TR sensor has a set of Hall-effect sensors that have a pattern of ON/OFF states which are dependent on the PARK, REVERSE, NEUTRAL, DRIVE, 3,
2 or 1 position of the manual valve.
The TR sensor also provides signals for the starting system and the reverse lights.
The PCM uses the TR sensor signal as an input for its strategy for shifting and TCC operation. The PCM also uses the TR sensor signal for transmission fault detection and diagnostics.
Transmission Operation Overview
Transmission operation is controlled by the PCM.
Torque Converter
This transmission uses a torque converter with the following elements:
- Impeller
- Turbine
- Reactor
- TCC
For diagnostic information, Refer to: Torque Converter Clutch (TCC) .
Planetary Gearsets
Operation of this transmission involves the use of 2 planetary gearsets that have the following components:
- Front (single planetary gearset)
- One sun gear
- One planetary carrier with 4 gears
- One ring gear
- Rear (ravigneaux planetary gearset)
- Two sun gears of different sizes
- Three short planetary gear pinions meshing with the sun gears
- Three long planetary gear pinions meshing with the sun gears
- One planetary carrier
- One ring gear
Hydraulic System
The hydraulic operation of this transmission includes the following components:
- Main control assembly
- Pump assembly with filter
- Torque converter
- Apply components (clutches)
Transmission Operation Overview
The PCM controls the operation of this transmission with the following solenoids:
- LPC solenoid
- SSA
- SSB
- SSC
- SSD
- SSE
- TCC solenoid