Index Land Rover Range Rover Automatic Transmission - manual 1997 year

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Range Rover Automatic Transmission. Manual - part 1

Range Rover

Automatic

Transmission

System Information

Document

APPLICABILITY

1995-1997 Range Rover

DATE OF REVISION

1997

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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

DOES VEHICLE MOVE ?

IS MIL ON P1775?

REFER TO ELECTRICAL

DIAGNOSIS

PAGES 8 THRU 24

YES

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.

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Schematic 1

MV1

MV2

TC LOCK

PRESSURE

17 34

MIL

Instrument Pack

C31

A27

A29

C27

A23

A22

BeCM

GEMS

Serial Link

H Gate C617

X Y Z

ehicle Speed

Engine Speed

MIL

Fuel Level

P1607

P0460/1

( )

ABS

TCU C603

TCM

32 31

Output Shaft

Speed Sensor

Motor Encoder

(ECU 2/28) (1/9/10)

Front

Rear

Road Wheel Sensors

(30/31)

(20)

(6)

(7)

(13)

(22)

(24/27)

Output Shaft

Speed Sensor

Fuel Level

Sensor

orque

Throttle Angle

ransfer Fault

orque SP

Reduction Speed

(23) P1775/6/7

(5/12)

(26)

P1701/3/8

REG.

MES

ehicle Speed

( ) P0500

C114

PIN 11

Rough Road Misfire

Detection Inhibit

P1317/8

C112

PIN 13

C112

PIN 9

C114

PIN 5

C112

PIN 14

Engine Speed

( ) (21)

Fuel Level

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)

C626

PIN 1

C626

PIN 12

DIAG ‘L

’

DIAG ‘K’

HI/LOW

C23

C255

PIN 8

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.

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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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