Range Rover Automatic Transmission. Manual - part 9

System Information Document

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[ZF_4SPD\Project_Specs]

[Revision:   2.3]

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© Rover Group 1998

Page 7 of 52

If the battery supply is different from that expected, the following details the functionality of the
transmission controller:

Voltage

System behaviour

16.0

-

26.0

Jump start; excess voltage without damage, limphome mode, output stanges for
solenoid valves and pressure regulator switched off (max 1min at 40

°

C).

9.0

-

16.0

Voltage range for normal operation of the EAT with CAN-Bus corresponding to the
specification.

6.5

-

9.0

Operation of the EAT with diagnostic functions and CAN-Bus enabled, limp home
mode, output stages for solenoid valves and pressure regulator switched off.

3.0

-

6.5

Under voltage with data retention in SRAM, limp home mode, unreliable
communication over the CAN bus.

0

-

3.0

Undervoltage without reliable function

-14

-

0

Reversed polarity without damage (-14V max 1 min at 25

°

C)

- Recommended wire size:

1.5mm

2

2.2.3 Serial information - inputs

2.2.3.1 Pins 16 and 44 - CAN information from Engnine management system

Both Discovery Series II and 99MY Range Rover vehicles use a CAN specification owned by ZF called
CAN 22H.  This communication protocol operates at 500kBit/sec. Both the engine management system
and the transmission controller should be fitted with 120

Ω

 terminating resistors.  For more information

on the CAN bus, please refer to the CAN specification.

2.2.4 Serial information – outputs

2.2.4.1 Pins 16 and 44 - CAN information sent to Engine Management system

See section the relevant section - CAN information from the Engine management system.

2.2.5 Digital inputs

2.2.5.1 Pins 8, 9, 36, 37 - Position switch

The position switch is the electrical input to the Transmission ECU regarding the drivers requested gear.
It is not however, exactly the same as the gear which the Transmission may have selected.  The
transmission assumes a new selector position has been selected after it has recognised a stable input /
code from the position switch lines for a filter time TPO_FILT.

System Information Document

____________________________________________________________________________________________________
_
[ZF_4SPD\Project_Specs]

[Revision:   2.3]

____________________________________________________________________________________________________
_
© Rover Group 1998

Page 8 of 52

Discovery Series II (GS8.87.0):

A 12V supply is required to the position switch whenever there is an ignition feed to the Transmission
controller.  If this is not realised, the transmission will be unable to function correctly and so limphome
mode will permanently be selected.  The movement of the gear lever will make or break with 4 different
sliding contacts.  This creates a coded representation of the selected gear.  These 4 wires go directly to
the Transmission ECU (Terminals L1, L2, L3 and L4) where they are decoded.  The software will then
decide if the selected gear can be safely engaged without damage to the Transmission and Engine.

- Component

- Type

Make contact to +12V

- Location

Gearbox, assembled together with the switch block

- Positions

Mechanical

P R N D 3 2 1

Hydraulic

P R N D 1

Electrical

P R N D 3 2 1 Z

- Control Unit

- Interface characteristic

Digital input, acitve high

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

U_low to U_high >= U_high to U_low + 0.5V

- Input circuit

(1.15 +/- 0.2) k

Ω

 (pull down to Ground)

- Input current

12.2 mA; input shorted to U_batt = 14V, R_in = 1.15 k

Ω

- Reference point

U_batt, pin 54

- 

Coded position inputs (a 1 represents a high potential, pulled high by the position switch)

Position

Switch

ECU

Pin

P

Z1

R

Z1

N

Z2

D

Z3

3

Z4

2

Z4

1

Line 1 (W)

36

1

1

0

1

1

1

1

1

0

0

0

0

0

Line 2 (X)

8

0

1

1

1

1

0

0

1

1

0

0

0

0

Line 3 (Y)

37

0

0

0

0

1

1

1

1

1

1

0

1

1

Line 4 (Z)

9

0

0

0

0

0

0

1

1

1

1

1

1

0

System Information Document

____________________________________________________________________________________________________
_
[ZF_4SPD\Project_Specs]

[Revision:   2.3]

____________________________________________________________________________________________________
_
© Rover Group 1998

Page 9 of 52

99MY Range Rover (GS8.87.1):

The position switch feed must be attached to ground at all times.  If this is not realised, the transmission
will be unable to function correctly and so limphome mode will permanently be selected.  The movement
of the gear lever will make or break with 3 different sliding contacts.  This creates a coded representation
of the selected gear.  These 4 wires go directly to the Transmission ECU (Terminals L1, L2 and L3)
where they are decoded.  The software will then decide if the selected gear can be safely engaged without
damage to the Transmission and Engine.

- Component

- Type

Make contact to Ground

- Location

Gearbox, assembled together with the switch block

- Positions

Mechanical

P R N D 3 2 1

Hydraulic

P R N D 1

Electrical

P R N D 3 2 1 F

- Control Unit

- Interface characteristic

Digital input, acitve low

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

U_low to U_high >= U_high to U_low + 0.5V

- Input circuit

(1.21 +/- 0.2) k

Ω

 (pull up to U_batt)

- Input current

-11.2 mA; input shorted to Ground, R_in = 1.21 k

Ω

- Reference point

Digital ground, pin 28

- 

Coded position inputs (a 0 represents a low potential, pulled low by the position switch)

Position

Switch

ECU

Pin

P

R

N

D

3

2

1

Line 1 (W)

36

0

0

1

1

0

0

0

Line 2 (X)

8

1

0

0

0

0

1

1

Line 3 (Y)

37

1

1

1

0

0

0

1

System Information Document

____________________________________________________________________________________________________
_
[ZF_4SPD\Project_Specs]

[Revision:   2.3]

____________________________________________________________________________________________________
_
© Rover Group 1998

Page 10 of 52

2.2.5.2 Pin 13 - High / Low range input

Discovery Series II (GS8.87.0):

The high / low range switch is electrically connected both to the transfer box and the EAT.  It sets the
transmission ratio of the transfer box and indicates the selected range to the EAT.

The closed switch indicates Low range, and open switch indicates high range.  After a change of the
signal (a rising or falling edge), the EAT ratains the signal vaue before the change for the applicable time
THL_WAIT.

- Component

- Type

Make contact to ground

- Location

Centre console

- Switch open

High range

- Switch closed (to ground)

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