Range Rover Automatic Transmission. Manual — part 1
© Rover Group 1997
Range Rover
Automatic
Transmission
System Information
Document
APPLICABILITY
1995-1997 Range Rover
DATE OF REVISION
1997
1-13
Operation Pride
See page 8 for SRO and time for
Electrical Symptom diagnosis
The diagnosis of automatic transmission faults requires that the technician take a systematic ap-
proach to the determination of the fault involved. There are two systems involved; the mechanical
operation of the transmission and the electronic control of the transmission via the Transmission
Control Module (TCM). It is important to realize that a mechanical problem can set a Diagnostic
Trouble Code (DTC) and also that an electronic failure can produce a mechanical symptom.
The following flowchart will help to direct you to the area requiring investigation first.
The information following the chart is split into 2 key areas:
System Information
Electrical Symptoms
NO
DOES VEHICLE MOVE ?
IS MIL ON P1775?
REFER TO ELECTRICAL
DIAGNOSIS
PAGES 8 THRU 24
YES
YES
NO
MECHANICAL PROBLEM
SEEK HELP LINE
ASSISTANCE IF NECESSARY
Mechanical Controls
The ZF 4HP22/24 automatic transmission is basically the same as the previous ZF automatic
transmission with the addition of electronic control over the pressure regulator, torque converter
lockup and shift valves.
Mechanical selection of Park, Reverse, Neutral and Drive is the same on both Mechanical and
Electronic Transmissions. This allows the vehicle to be operated in Limp Home Mode if the elec-
tronic controls fail. The mechanical diagnosis of the transmission is the same as before and would
require the same repair procedure.
Electronic Controls
Refer to the following schematic to graphically demonstrate the interconnection of the various
control units used in the operation of the electronically controlled transmission.
1-13
Operation Pride
Schematic 1
MV1
MV2
TC LOCK
PRESSURE
L
R
L
R
32
15
17 34
18
35
16
33
KR
KU
KN
KB
BG
N
B
N
B
N
B
N
B
MIL
Instrument Pack
C4
C31
A27
A29
C27
A23
A22
C7
BeCM
GEMS
Serial Link
H Gate C617
X Y Z
V
ehicle Speed
Engine Speed
MIL
Fuel Level
P1607
P0460/1
( )
( )
ABS
TCU C603
TCM
19
17
32 31
7
30
13
50
29
Output Shaft
Speed Sensor
Motor Encoder
14
19
5
24
42
6
20
2
38
32
47
21
3
(ECU 2/28) (1/9/10)
Front
Rear
Road Wheel Sensors
R
U
(30/31)
(20)
(6)
(7)
(13)
(22)
(24/27)
1
2
3
Output Shaft
Speed Sensor
Fuel Level
Sensor
T
orque
Throttle Angle
YO
T
ransfer Fault
T
orque SP
Reduction Speed
(23) P1775/6/7
(5/12)
(26)
P1701/3/8
REG.
46
29
MES
31
16
28
29
V
ehicle Speed
( ) P0500
C114
PIN 11
28
C1
Rough Road Misfire
Detection Inhibit
P1317/8
C112
PIN 13
C112
PIN 9
C114
PIN 5
C112
PIN 14
8
10
7
6
5
4
3
33
Engine Speed
( ) (21)
Fuel Level
P1
199/P0460/1 97 MY
MES 1
MES 2
C626
PIN 18
C626
PIN 9
C626
PIN 8
C626
PIN 5
C626
PIN 16
C626
PIN 11
C114
PIN 10
PARK
NEUTRAL
POSITION
SWITCH
(PNPS)
15
51
A
C626
PIN 1
C626
PIN 12
DIAG ‘L
’
DIAG ‘K’
A
35
HI/LOW
C23
13
C255
PIN 8
14
C255
PIN 17
DIAG ‘L
’
DIAG ‘K’
PIN 7
PIN 15
DLC
C231
Note: A number preceded by a P, for example P1775, relates to fault codes stored in GEMS if
the signal/component fails.
A number in parenthesis, for example (23), relates to fault codes stored in the TCM if the
signal/component fails.
1-13
Operation Pride
Economy, Sport and Manual Modes
The TCM has various different driving modes available, with Economy being selected automati-
cally on start up. When the vehicle is in High range, Sport mode can be selected. Sport mode
makes gear change much more sensitive to throttle movement, thereby shifting down earlier and
holding onto lower gears longer than Economy mode. If the vehicle is in Low range, then the
manual mode can be selected. Manual mode will make the transmission change to the gear se-
lected as quickly as possible and hold onto that gear at all speeds, i.e. if “3” is selected, then the
gear box will not shift down to “2” or “1” as the vehicle slows down. It will only shift down to pre-
vent the vehicle from stalling.
In addition to the manual mode of operation in low range, the Economy mode is also different
than that of the High range Economy mode. This Economy mode has to be different because of
the low ratio the transfer box employs, thus causing a torque multiplication, which increases the
need to change the shift points and ignition retard points. The shift points will also be modified by
the vehicle speed in relation to the engine rpm to ensure shifts at the best points for fuel economy.
Interface with Engine Control Module (ECM), see schematic 1
The TCM takes the engine torque, engine speed and throttle angle signals from the ECM and cal-
culates which gear is required. The TCM then provides outputs to the solenoid valves and sends
a torque reduction signal back to the ECM. The ECM then retards the ignition point on each of the
cylinders, resulting in a reduction in engine power to produce smoother shifts.
If the TCM detects a fault that affects emissions levels, the TCM has the ability to output a “Check
Engine” request to the ECM. The TCM does this by sending a signal to the ECM on the ignition
retard request line. When the ECM receives this signal, it knows that it is a request to illuminate
the “Check Engine” light and not a ignition retard request. The reason the ECM handles the
“Check Engine” request is because the TCM does not have the ability to illuminate a “Check
Engine” light directly.
When the ECM receives this signal, it will flag a DTC P1775 immediately and illuminate the
“Check Engine” light.
Interface with TCM and Park Neutral Position Switch (PNPS), see schematic 1
The PNPS is mounted on the side of the transmission and contains five internal switches, al-
though only three, known as the “XYZ” switches, are used by the TCM. The other two switches
are for reverse selection and start inhibit, neither of which is required by the TCM. By analyzing
the status of the “XYZ” switches, the TCM calculates which gear has been selected. If a fault oc-
curs with a switch, the TCM may try to put the transmission into a different gear than requested.
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