Transmission Electronic Control System
Transmission Electronic Control System
Transmission Control Module (TCM) 4.6L/5.4L
For vehicles equipped with a 4.6L or 5.4L engine, the Transmission Control Module (TCM) controls the functions of this transmission. The TCM is part of a molded plastic leadframe module that is bolted to the mechatronic assembly. The leadframe module also has the Turbine Shaft Speed (TSS), Output Shaft Speed (OSS), Transmission Range (TR) and Transmission Fluid Temperature (TFT) sensors integrated into it.
The TCM responds to inputs from the sensors and from the vehicle Controller Area Network (CAN) system. The TCM uses the inputs to control the line pressure, shift and TCC solenoids. The TCM also provides power and ground for the reverse lamp relay coil and provides a PARK/NEUTRAL start enable signal.
The TCM uses the following inputs from the vehicle CAN system:
- Engine speed
- Engine torque
- Engine Coolant Temperature (ECT)
- Engine Oil Temperature (EOT)
- Throttle Position (TP)
- Accelerator Pedal Position (APP)
- Brake Pedal Position (BPP)
- ABS wheel speed
- Automatic Traction Control (ATC) status
- Four-Wheel Drive (4WD) status
The TCM also:
- monitors inputs and outputs for the presence of faults.
- stores DTCs related to detected faults.
- supplies outputs to the vehicle CAN for TR position, OSS, TSS, TFT, current gear and A/C inhibit.
- provides On-Board Diagnostic (OBD) information using the CAN system to illuminate the Malfunction Indicator Lamp (MIL) or Transmission Control Indicator Lamp (TCIL).
- displays diagnostic information to a scan tool through the Data Link Connector (DLC).
Transmission Control Module (TCM) Leadframe
If the TCM detects a fault, it uses Failure Management and Effects Mode strategies to substitute a value or signal.
The TCM also uses Failure Management and Effects Mode strategies to compensate for detected solenoid or apply component faults that result in alternate shift patterns.
If the transmission loses complete electronic control, it will operate in a failsafe 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
Solenoid Application Chart
a PCM or transmission control module (TCM) controlled
PCM 6.2L
For vehicles equipped with a 6.2L engine, the PCM and its input/output network control the following transmission operations:
- Shift timing
- Line pressure (shift feel)
- Torque Converter Clutch (TCC)
The transmission control strategy is separate from 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 sensors and switches.
In addition, the PCM receives input signals from transmission sensors and switches. The PCM will also use these signals when determining transmission operating strategy.
Using all of these inputs, the PCM can determine when the time and conditions are right for a shift, or when to apply or release TCC. The PCM will also determine the best line pressure needed to optimize shift feel. To accomplish this, the PCM uses solenoids to control transmission operation.
The PCM also:
- monitors inputs and outputs for the presence of faults.
- stores DTCs related to detected faults.
- supplies outputs to the vehicle CAN for TR position, OSS, TSS, TFT, current gear and A/C inhibit.
- provides On-Board Diagnostic (OBD) information using the CAN system to illuminate the Malfunction Indicator Lamp (MIL) or Transmission Control Indicator Lamp (TCIL).
- displays diagnostic information to a scan tool through the Data Link Connector (DLC).
Molded Leadframe
If the PCM detects a fault, it uses Failure Management and Effects Mode strategies to substitute a value or signal.
The PCM will use Failure Management and Effects Mode strategies to compensate for detected solenoid or apply component faults that result in alternate shift patterns.
If the transmission loses complete electronic control, it will operate in a failsafe 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
The following provides a brief description of each of the sensors and actuators used to control transmission operation.
Line Pressure Control (LPC) Solenoid
The Line Pressure Control (LPC) solenoid is a Variable Force Solenoid (VFS) that varies hydraulic pressure by actuating a hydraulic valve.
The PCM or TCM applies variable current to the LPC solenoid which varies pressure in the VFS5 hydraulic circuit to the Main Regulator Valve. Refer to Hydraulic Circuits Hydraulic Circuits for information.
The LPC solenoid uses inversely proportional operation. As the current from the PCM or TCM decreases, the pressure from the solenoid increases. As the current from the PCM or TCM increases, the pressure from the solenoid decreases. The LPC solenoid is supplied hydraulic pressure from the SREG circuit.
With zero current, the LPC solenoid fully opens the hydraulic valve which applies the maximum amount of hydraulic pressure to the Main Regulator Valve through the VFS5 hydraulic circuit and applies maximum line pressure in the PUMP hydraulic circuit. With maximum current to the solenoid, the hydraulic valve fully closes the outlet port for minimum pressure to the VFS5 hydraulic circuit to lower the line pressure in the PUMP hydraulic circuit.
Line Pressure Control (LPC) Inversely Proportional Variable Force Solenoid (VFS)
Torque Converter Clutch (TCC) Solenoid
The TCC solenoid is a VFS that varies hydraulic pressure by actuating a hydraulic valve.
The PCM or TCM 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. Refer to Hydraulic Circuits Hydraulic Circuits.
The TCC solenoid uses proportional operation. As the current from the PCM or TCM decreases, the pressure from the solenoid decreases. As the current from the PCM or TCM 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.
Torque Converter Clutch (TCC) Proportional Variable Force Solenoid (VFS)
Shift Solenoid A (SSA), Shift Solenoid B (SSB), Shift Solenoid C (SSC) and Shift Solenoid D (SSD)
Shift solenoids A through D are variable force type solenoids that vary hydraulic pressure by actuating a hydraulic valve.
The PCM or TCM 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. Refer to Hydraulic Circuits Hydraulic Circuits.
Shift Solenoid A (SSA) and Shift Solenoid C (SSC) use proportional operation. As the current from the PCM or TCM decreases, the pressure from the solenoid decreases. As the current from the PCM or TCM 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 A (SSA) and Shift Solenoid C (SSC) Proportional Variable Force Type Solenoids
Shift Solenoid B (SSB) and Shift Solenoid D (SSD) use inverse proportional operation. As the current from the PCM or TCM decreases, the pressure from the solenoid increases. As the current from the PCM or TCM 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 Solenoid B (SSB) and Shift Solenoid D (SSD) Inverse Proportional Variable Force Type Solenoids
Shift Solenoid E (SSE)
Shift Solenoid E (SSE) is an ON/OFF solenoid. When SSE is in the OFF position, SSD controls the regulator and latch valves to apply the low/reverse clutch. When SSE is in the ON position, SSD controls the regulator and latch valves to apply the Overdrive (O/D) (456) clutch. Refer to Hydraulic Circuits Hydraulic Circuits.
SSE is supplied hydraulic pressure from the SREG circuit. When SSE is OFF, the solenoid supply is blocked and the outlet port (SS1 circuit) is connected to the exhaust port. When SSE is ON, the exhaust port is blocked and the solenoid supply is connected to the outlet port (SS1 circuit).
Shift Solenoid E (SSE) ON/OFF Solenoid
Turbine Shaft Speed (TSS) Sensor
The TSS sensor is a Hall-effect type sensor that provides a signal to the PCM or TCM that changes in frequency as the rotating speed of the forward (1234) clutch cylinder varies.
The PCM or TCM compares the TSS sensor signal with the engine speed information to determine the amount of slip occurring in the torque converter.
The PCM or TCM also compares the TSS sensor signal with the OSS sensor signal to determine the gear ratio provided by the rear planetary gearset.
The PCM or TCM uses the TSS sensor signal as an input for its strategies for shifts and TCC operation. The PCM or TCM also uses the TSS sensor signal for transmission fault detection and diagnostics.
Refer to the component illustration at the beginning of this procedure for the location of the TSS sensor.
Output Shaft Speed (OSS) Sensor
The OSS sensor is a Hall-effect type sensor that provides a signal to the PCM or TCM that changes in frequency as the rotating speed of the output shaft ring gear varies.
The PCM or TCM also compares the OSS sensor signal with the TSS sensor signal to determine the gear ratio provided by the rear planetary gearset.
The PCM or TCM uses the OSS sensor signal as an input for its strategies for shifts and TCC operation. The PCM or TCM also uses the OSS sensor signal for transmission fault detection and diagnostics.
Refer to the component illustration at the beginning of this procedure for the location of the OSS sensor.
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 or TCM monitors the voltage across the TFT sensor, which changes as TFT varies.
The PCM or TCM uses the TFT sensor signal as an input for its strategy for shifting and TCC operation. The PCM or TCM also uses the TFT sensor signal for transmission fault detection and diagnostics.
Refer to the component illustration at the beginning of this procedure for the location of the TFT sensor.
Transmission Range (TR) Sensor
The TR sensor has a set of Hall-effect sensors that have a pattern of ON/OFF states which are dependant 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 or TCM uses the TR sensor signal as an input for its strategy for shifting and TCC operation. The PCM or TCM also uses the TR sensor signal for transmission fault detection and diagnostics.
Refer to the component illustration at the beginning of this procedure for the location of the TR sensor.