Description and Operation (F21): Description

Adoption Of Integrated Position Sensor With TCU

The shift position sensor is integrated in TCU. TCU indicates a shift position by reading a voltage difference between output voltages (Pos1, Pos2) from the shift position sensor.

Fig 1: Identifying Shift Position Sensor

Courtesy of HYUNDAI MOTOR CO.

Function Of TCU

Automatic gear shift control
In automatic gear shift control, based on each gear shift pattern, S1 and S2 turn on or off and SLC1, SLC2, SLC3, and SLB1 are operated linearly according to information that includes vehicle speed, Throttle valve opening degree, and brake signals.
Lock-up control
Based on RPM signals, signals from the engine control unit (engine RPM and throttle opening) and vehicle speed, smooth lockup control is achieved through linear control of the lock-up control solenoid (SLU). (However, this assumes that JWS-3309 < T-IV > is used.)
Garage shift control
When the shift lever is moved from N to D or from N to R, after the engine is started, a shift control solenoid (SLC1, SLC3) is used for the oil pressure required by C1 clutch or C3 clutch and appropriately regulated oil pressure is supplied to the clutch, engaging smoothly without shock.
NOTE:
- When the engine is cold, the first piston stroke resistance increases, creating a time lag in shift operation. In order to reduce the time lag, control is not performed.
- By controlling the oil pressure according to the piston stroke, smooth engagement without shock becomes possible.
Reverse control
If the shift lever is moved from N to R while the vehicle is traveling and the transmission shifts into reverse, the wheels may be locked, which is extremely dangerous. In order to avoid this, TCU inhibits the transmission from shifting into reverse while traveling.
NOTE:
- Even when the shift lever is moved from N to R, the transmission does not shift into reverse if the vehicle speed is 11 km/h or more.
- When this control is activated, the C3 clutch is released without operating the shift control solenoid (SLC3) so that the transmission does not shift into reverse.
- Reverse control takes precedence over N-R shift control.
Self-diagnosis function
The TCU monitors the communication status of each sensor, electronic component and ECU including the engine control unit. If any malfunction should occur, the TCU functions to warn the driver and stores the malfunction as a diagnosis code.

Fail-safe

With the fail-safe function, if any malfunction should occur in the automatic transmission system, the TCU will output a control signal, and control will be performed to make traveling a minimum distance possible. If shift solenoid malfunction, the TCU will cancel the output of control signals to the solenoid. If this happens, automatic transmission gear shifting will be controlled by oil pressure circuits only and the gears will shift as shown in the chart below.

SHIFT POSITION SPECIFICATION

Shift position	Gear position
R	Reverse
D	3rd gear (5th gear in case of SLC1 failure)

Driver adaptive shift control

The F21 for HMC does not have a driving mode selection switch that allows drivers to select a mode themselves. The vehicle is ordinarily in economy mode. However, when specific conditions are met, the TCU selects a shifting pattern appropriate to driving conditions from all of the shifting patterns and switches automatically.

MODE DESCRIPTION

Mode	Description
ECONOMY	Used during normal driving. ECONOMY mode is basic shift schedule and the ideal shift schedule to be consistent with fuel economy and acceleration performance. This mode is normally selected where no other higher priority shift mode is activated. Full shift schedule map is available including lockup for this mode.
HIGH OIL TEMPERATURE (HOT)	This mode is protect the gearbox from the overheating. This mode is activated where the T/M oil temperature is too high, and will prevent the T/M oil temperature increasing by torque converter slipping. HOT shift schedule maps is available including lockup depending on the T/M oil temperature area for this mode.
MANUAL SHIFT MODE	The manual shift mode is activated where the driver put the shifter into manual gate. The gear position is manually changed according to the driver shift demand. The automatic down shift function in decelerating and automatic up shift function for engine over revolution protection are available. The allowable vehicle speed for up shifting at low vehicle speed and down shifting at high speed set be TCU parameters.
UP-SLOPE (US1, 2)	The UP-SLOPE1, 2 mode detect up hill road condition and change the shift map to powerful map to avoid busy shifting at up hill condition. When start condition of up slope mode is detected, shift map is changed upslope1 or upslope2 map depending on slope gradient if no higher priority mode is activated.
AUTO CRUISE CONTROL (ACC)	The AUTO CRUSE CONTROL detects "ACC ON" signal and use specific point to prevent shift hunting during ACC ON. When cruise control is ON, gears are fixed to perform smooth driving.
GEAR HOLD	The GEAR HOLD according to the request by ESP in order to support the vehicle stability. This function can be activated in every shift mode except for MANUAL SHIFT MODE. When start condition is fulfilled, gear is held to current gear. The gear hold is performed after shift control finished if start condition is fulfilled during shifting.

Mode Priority On Current Implementation

MODE PRIORITY

Mode priority	Shift mode
Courtesy of HYUNDAI MOTOR CO.	MANUAL SHIFT MODE
	GEAR HOLD
	HOT
	UP-SLOPE 2
	UP-SLOPE 1
	AUTO CRUISE CONTROL
	ECONOMY