Land Rover Discovery: External Controls / Description and Operation

COMPONENT LOCATION

1. Downshift paddle switch
2. Upshift paddle switch
3. Transmission Control Switch (TCS)

OVERVIEW

The external controls comprise a rotary TCS (transmission control switch) and two steering wheel mounted paddle switches.

The TCS transmits driver transmission selections to the TCM (transmission control module) for transmission mode selections. The paddle switches allow the driver to initiate gear shifts in all transmission modes; 'D' drive, 'S' manual CommandShift.

DESCRIPTION

TRANSMISSION CONTROL SWITCH

The TCS is a rotary switch installed in the floor console and controls the driver transmission selections.

The TCM allows the transmission to be operated as a conventional automatic unit by selecting P R N D on the TCS. Rotation of the TCS allows the selection of P R N D S. Depressing and rotating the TCS clockwise from the D position, S mode can be selected. The TCS is a fully electronic rotary transmission switch with no mechanical connection to the transmission.

Mechanical operation of the transmission corresponding to selections made on the TCS is performed by the TCM on the transmission casing.

For additional information, refer to: Transmission Description (307-01, Description and Operation).

The TCS rises from its housing once the engine is running. When the engine is stopped, with the TCS in any position other than 'N', it retracts into the housing again. If the TCS is in position 'N' when the engine is stopped, it remains in the raised position for up to 10 minutes, for use in a drivethrough car wash for example. After 10 minutes the TCS automatically retracts. The TCS also retracts if 'P' is selected within the 10 minute period.

If the TCS does not rise from the housing when the engine is started, but electrical power is supplied to the TCS, the retracted TCS can still be rotated to make selections.

If electrical power to the TCS is lost, the TCS will not rise from the housing when the engine is started and the retracted TCS cannot be rotated. The TCS contains an internal shift lock solenoid to prevent the switch from being rotated when the engine is not running.

The engine can be stopped with the TCS in any position. Once the engine is stopped the switch will automatically reset to the 'P' position and the transmission Park lock will be engaged, except if the TCS is in the 'N' position when the engine is stopped.

LED (light emitting diode)'s on the TCS illuminate to display the selected position. If the brake pedal is not depressed when a selection is made, the selected position LED flashes and the mode selection is not performed.

PADDLE SWITCHES

Two gear change paddle switches are fitted at the rear of the steering wheel and allow the driver to operate the transmission as a semi-automatic manual transmission using the CommandShift feature. Each paddle switch has three connections; ground, illumination PWM (pulse width modulation) supply and ground switch signal.

The left paddle switch (-) controls the downshifts and the right paddles switch (+) controls the upshifts.

EMERGENCY PARK RELEASE

The 'shift by wire' control system has no mechanical or electrical EPR provision to remove the vehicle from Park in the event of a system fault.

The Service Park Release (SPR) procedure must be used to rotate the transmission selector shaft manually to the 'N' (Neutral) position. Refer to the relevant service procedure or the Automatic Transmission Description and Operation section.

For additional information, refer to: Transmission Description (307-01, Description and Operation).

OPERATION

TRANSMISSION CONTROL SWITCH (TCS)

Rotation of the TCS to any of the five positions is sensed by the TCM via the high speed CAN (controller area network) powertrain systems bus. The TCM reacts according to the selected position if all parameters for that selection are met.

The TCS has a magnetic system using Hall effect sensors to determine the position of the switch. The 'S' (Sport) position selection allows the TCM to operate the transmission as a semi-automatic 'CommandShift' system.

Gear selections are sensed by the TCM when the driver operates the steering wheel paddle switches. Once the TCS position is confirmed, the TCS outputs applicable information on the high speed CAN powertrain systems bus, which is received by the TCM to activate the correct gear and by the instrument cluster to display the selected mode or gear in the instrument cluster message center

The paddle switches can be used on a temporary basis when the TCS is in the 'D' (Drive) position to override the automatic gear selection if required.

PADDLE SWITCHES

The paddle switches are hardwired to the speed control switch on the steering wheel. Operation of a paddle switch completes a ground path to the speed control switch. The speed control switch converts the completed ground signal into a LIN (local interconnect network) signal which is passed via the clockspring to the CJB (central junction box). The CJB converts the signal into a high speed CAN powertrain systems bus signal to the TCM.

Pulling the left downshift (-) paddle switch provides down changes and pulling the right upshift (+) paddle switch provides up changes. The first operation of either paddle switch, after 'S' sport mode is selected, puts the transmission into permanent manual CommandShift. Rotation of the TCS back to the 'D' (Drive) position returns the transmission to conventional automatic operation.

Temporary operation of CommandShift mode can also be operated with the TCS in the 'D' (Drive) position. Operation of either the upshift or downshift paddle switches activates the manual CommandShift mode operation. If the TCS is in 'D' (Drive), CommandShift will cancel after a time period or can be cancelled by pressing and holding the upshift (+) paddle switch for approximately 2 seconds.

The operation of the paddle switches is configurable by the driver using the menu in the instrument cluster. The menu allows the driver to select operation of the paddle switches in 'S' (Sport) only (default setting for NAS and China market vehicles) or in 'D' (Drive) and 'S' (Sport) (default setting all other markets).

NEUTRAL AND SHIFT LOCK

The shift lock strategy is controlled by the TCM. Shift lock is activated when the TCS is in 'P' or 'N' and the engine is running.

The shift lock is a requirement for the TCS. The switch is always locked at ignition on (power mode 6) when the engine is not running, except after an engine stall when the selector is not in 'P' (Park) or 'N' (Neutral). If, when driving with the TCS in 'S' (Sport), 'D' (Drive) or 'R' (Reverse) at a speed of more than 10 km/h (6 mph), the driver selects 'P' (Park) or 'N' (Neutral) without the brake pedal depressed, the TCS will be immediately locked once the vehicle speed falls to below 10 km/h (6 mph).

With the brake pedal pressed, the TCS will remain unlocked for as long as the brake pedal remains pressed, regardless of vehicle speed. The TCM will only engage the shift lock once the vehicle speed is less than 10 km/h (6 mph). If the driver selects 'N' and releases the brake pedal with a vehicle speed of less than 10 km/h (6 mph), the TCS will be locked 2 seconds after 'N' (Neutral) is selected. The TCS will remain locked until the driver presses the brake pedal again.

CONTROL DIAGRAM

NOTE:

A = Hardwired; O = LIN Bus; AN = High speed CAN powertrain systems

1. Transmission Control Module (TCM)
2. Central Junction Box (CJB)
3. Transmission Control Switch (TCS)
4. Engine Control Module (ECM)
5. Anti-lock Brake System (ABS) control module
6. Instrument Cluster (IC)
7. Clockspring - paddle switch inputs
8. Valve block
9. Transmission Control Switch (TCS)
10. Ground
11. Fuse - ignition supply from ignition relay
12. Ignition relay (CJB)
13. Fuse - Permanent battery supply

External ControlsExternal Controls / Diagnosis and Testing

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