Discovery 2. Manual — part 145
AUTOMATIC GEARBOX - ZF4HP22 - 24
DESCRIPTION AND OPERATION
44-11
2nd Gear (D selected)
Clutches (4), (6), (7) and (11) are engaged. Freewheel (15) overruns. The hollow shaft with the sun wheel of gear set
(9) is locked. Gear set (10) also rotates as a solid unit.
3rd Gear (D selected)
Clutches (4), (5), (7) and (11) are engaged. Freewheels (15) and (16) are overrun. Gear sets (9) and (10) rotate as a
solid unit.
4th Gear (D selected)
Clutches (4), (5), (7) and (12) are engaged. Freewheels (14), (15) and (16) are overrun. Gear set (9) rotates as a solid
unit. The hollow shaft with the sun wheel of gear set (10) is locked.
AUTOMATIC GEARBOX - ZF4HP22 - 24
44-12
DESCRIPTION AND OPERATION
Reverse gear
Clutches (5), (8) and (11) are engaged. The front planet gear carrier of gear set (9) is locked. Gear set (10) also rotates
as a solid block.
Gear position switch
The gear position switch outputs signals that are related to the position of the selector lever assembly. The switch is
installed on the selector shaft on the left side of the gearbox. Slotted mounting holes allow the switch to be turned
relative to the shaft for adjustment. A fly lead connects the switch to the vehicle wiring.
Movement of the selector lever assembly turns the selector shaft, which operates six pairs of contacts in the switch.
The pairs of contacts are identified as the W, X, Y, Z, Park/Neutral and Reverse contacts. When closed:
l
The W, X, Y and Z contacts output a 12V ignition supply from the BCU.
l
The Park/Neutral contacts output an earth.
l
The Reverse contacts output a 12V ignition supply from the passenger compartment fuse box.
The outputs of the W, X, Y and Z contacts are monitored by the EAT ECU and the BCU to determine the position of
the selector lever assembly.
Gear position switch W, X, Y, Z outputs
The Park/Neutral contacts output to the BCU and, on diesel models, the ECM. The Reverse contacts output to the
BCU, the reversing lamps, the SLABS ECU and, where fitted, the ACE ECU and the electrochromic interior mirror.
Switch
contacts
Output
P
R
N
D
3
2
1
W
12V
-
12V
12V
-
-
-
X
-
12V
12V
-
12V
-
-
Y
-
-
12V
12V
12V
-
12V
Z
-
-
-
12V
12V
12V
-
AUTOMATIC GEARBOX - ZF4HP22 - 24
DESCRIPTION AND OPERATION
44-13
Oil cooler
1 Inlet connection
2 Fixing bracket
3 Outlet connection
4 Fixing bracket
5 Temperature sensor
Transmission fluid from the gearbox is circulated through a cooler attached to the front of the radiator. Quick release
connectors on the transmission fluid lines attach to connections on each end tank of the cooler. A temperature sensor
on the RH end tank provides the instrument pack with an input of transmission fluid temperature. If the temperature
exceeds a preset limit, the instrument pack illuminates the transmission temperature warning lamp. The warning lamp
remains illuminated until the temperature of the fluid returns within limits.
EAT ECU
The EAT ECU operates the solenoid valves in the gearbox to provide automatic control of gear shifts and torque
converter lock-up. The EAT ECU is attached to a protective bracket which is secured to the cabin floor below the LH
front seat. A 55 pin connector links the EAT ECU to the vehicle wiring.
Software in the EAT ECU monitors hard wired inputs and exchanges information with the ECM on a Controller Area
Network (CAN) bus to determine gear shift and torque converter lock-up requirements. Resultant control signals are
then output to the gearbox solenoid valves.
AUTOMATIC GEARBOX - ZF4HP22 - 24
44-14
DESCRIPTION AND OPERATION
EAT ECU connector
EAT ECU connector pin details
Pin No.
Description
Inputs/Outputs
1 to 4
Not used
-
5
Pressure regulator solenoid valve (MV 4)
Output
6
Power earth
-
7
Not used
-
8
Gear position switch, X contacts
Input
9
Gear position switch, Z contacts
Input
10 to 12
Not used
-
13
Transmission high/low switch
Input
14
Gearbox output shaft speed sensor, negative
Input
15
Gearbox output shaft speed sensor cable screen
-
16
CAN, high
Input/Output
17 to 24
Not used
-
25
Sport mode warning lamp
Output
26
Battery power supply
Input
27
Not used
-
28
Electronics earth
-
29
Not used
-
30
Shift control solenoid valve (MV 1)
Output
31
Diagnostics, K line
Input/Output
32
Converter lock-up solenoid valve (MV 3)
Output
33
Shift control solenoid valve (MV 2)
Output
34
Not used
-
35
Not used
-
36
Gear position switch, W contacts
Input
37
Gear position switch, Y contacts
Input
38 to 41
Not used
-
42
Gearbox output shaft speed sensor, positive
Input
43
Not used
-
44
CAN, low
Input/Output
45
Mode switch
Input
46 to 50
Not used
-
51
Manual mode warning lamp
Output
52
Not used
-
53
Solenoid valves power supply
Output
54
Ignition power supply
Input
55
Not used
-
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