Range Rover Automatic Transmission. Manual - part 10

System Information Document

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[ZF_4SPD\Project_Specs]

[Revision:   2.3]

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© Rover Group 1998

Page 11 of 52

99MY Range Rover (GS8.87.1):

The high / low range switch on 99My Range Rover is a component of the H-gate.  It is electrically
connected to the transfer box; the input signal to the EAT is generated in the control unit of the transfer
box.

A constant high signal indicates Low range, a constant low signal indicates high range.  When the range
is changing from Low range to High range, the transfer box ECU sends a periodic pulse whilst in the
neutral position.

After a change of the signal (ie a rising or falling edge), the EAT retains the signal value before the
change for the applicable time THL_WAIT.

- Component

- Type

Active low

- Location

Transfer box

- Signal open circuit / high

Low range

- Signal active / low

High range

- Control Unit

- Interface characteristic

Digital input, active low

- Threshold U_low to U_high=< 6.0V, U_OS_AD
- Threshold U_high to U_low=> 2.0V, U_US_AD
- Hysteresis

U_low to U_high => U_high to U_low +0.5V

- Input circuit

(1.2 +/- 0.2) k

Ω

 (pull up to Ubp)

- Input current

-10mA, input grounded, U_batt = 14V, R_in = 1.2k

Ω

- Reference

Digital ground, pin 28

System Information Document

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[ZF_4SPD\Project_Specs]

[Revision:   2.3]

____________________________________________________________________________________________________
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© Rover Group 1998

Page 12 of 52

2.2.5.3 Pin 45 - Driver mode request

Discovery Series II (GS8.87.0):

The program selector is used to select shift strategies depending on the setting of the High/Low range
switch.  The strategies can be selected independently for High range and Low range.  After ignition on
and after changing between High range and Low range, the EAT assumes a default shift strategy (normal
mode).

The number of implemented shift strategies can be individually set for High range and Low range by the
label KPG_MAX

The program selector is a push button that is debounced and latched by software in the EAT.  The EAT
changes the shift strategy after it has recognised the stable input voltage U_low for the time period
TPG_FILT

- Component

- Type

Make contact to ground

- Max bounce time

<= 50ms

- Location

facia or centre console

- Positions

Toggle between shift strategies

- Switching function

Normal - Sport (high range), Normal - Manual (low range)

- Control Unit

- Interface characteristic

Digital input, active low

- Threshold U_low to U_high=< 6.0V, U_OS_AD
- Threshold U_high to U_low=> 2.0V, U_US_AD
- Hysteresis

U_low to U_high => U_high to U_low +0.5V

- Input circuit

(1.2 +/- 0.2) k

Ω

 (pull up to Ubp)

- Input current

-10mA, input grounded, U_batt = 14V, R_in = 1.2k

Ω

- Reference

Digital ground, pin 28

99MY Range Rover (GS8.87.1):

The purpose of the program selector is to select shift strategies depending on the setting of the High /
Low range input.  The strategies can be selected independantly for High Range and Low Range.  After
ignition on and after changing between high range and low range, the EAT assumes a default shift
strategy (normal mode).

The number of implemented shift strategies can be inndividually set for high range and Low range by the
label KPG_MAX.

The program selector is a switch that is debounced and latch internally.  The EAT changes shift strategy
after it has recognised a stable input voltage for a time period TPG_FILT.

System Information Document

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[ZF_4SPD\Project_Specs]

[Revision:   2.3]

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© Rover Group 1998

Page 13 of 52

- Component

- Type

Make contact to ground

- Max bounce time

<= 50ms

- Location

H gate

- Positions

Toggle between shift strategies

- Switching function

Switch open, signal high = Normal
Switch closed, signal low = Sport (high range)
Switch closed, signal low = Manual (low range)

- Control Unit

- Interface characteristic

Digital input, active low

- Threshold U_low to U_high=< 6.0V, U_OS_AD
- Threshold U_high to U_low=> 2.0V, U_US_AD
- Hysteresis

U_low to U_high => U_high to U_low +0.5V

- Input circuit

(1.2 +/- 0.2) k

Ω

 (pull up to Ubp)

- Input current

-10mA, input grounded, U_batt = 14V, R_in = 1.2k

Ω

- Reference

Digital ground, pin 28

2.2.6 Digital outputs

2.2.6.1 Pin 25 and 51 - MES lines 1 and 2

The MES signal lines drive lights in the instrument pack that display the selected shift strategy and the
EAT’s fault state.  Pin 51 and Pin 25 are open drain outputs.  The following table shows the switching
function; a “0” represents a low output, a “1” represents a high output voltage.

MES 1 - Pin 51

MES 2 - Pin 25

Normal

1

1

Sport

0

1

Manual

1

0

Fault

0

0

- Component

- U_low

U < 1.2V

- U_high

U > U_batt - 3.0V

- R to U_batt

1.0k

Ω

- Control unit

- Interface characterisics

Digital output / open drain, active low

- U_low

<= 1.0V @ I = 30mA

- U_high

>= U_batt - 2.0V at I <= 0.5mA

- R to U_batt

1.21 k

Ω

N.B.

After reset and igniton on, the MES lines display “Normal” as the default strategy.

System Information Document

____________________________________________________________________________________________________
_
[ZF_4SPD\Project_Specs]

[Revision:   2.3]

____________________________________________________________________________________________________
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© Rover Group 1998

Page 14 of 52

2.2.7 Analogue inputs

2.2.7.1 Pins 14,15,42 - Output shaft speed sensor

The transmission output shaft speed is captured by an inductive sensor that is mounted at a magent wheel
with 36 teeth.  The signal is transmitted to the EAT over a shielded 2-wire connection.

- Component (inductive sensor)

- location

Gearbox housing

- output

36 pulses per revolution

- f_min

102Hz (170 rpm)

- f_max

5.0kHz (8333 rpm)

- sensor voltage Ui_min

0.7 Vs at 102Hz (peak voltage)

- sensor voltage Ui_max

1.3 Vs at 102Hz (peak voltage)

- sensor distance

0.85mm

- load resistance

R_1 = 20k

Ω

- Control unit

- Interface characteristic

Frequency input

- R_in Pin 14 to Pin 42

20k

Ω

- sensitivity U_min

1.2Vss (peak to peak) @  100 Hz

- sensitivity U_max

200 Vss @ 100 Hz

- f_max

6.0 kHz

- Rotational limit

- n_min

170 rpm

- n_max

8333 rpm

- Switching voltage of input (U @ Pin 42 - U @ Pin 14) /2

- Signal processing in the EAT

- The EAT calculates the mean period time over one program loop.