Land Rover Range Rover Electronic Arir Suspension Rover Manual

							EAS - System Information Document
© Rover Group 1998Page 1 of 32
Range Rover
Electronic Air
Suspension
APPLICABILITYto 98MY
DATE OF REVISION03/06/98 
						

							EAS - System Information Document
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Introduction
The electronically controlled air suspension (EAS) system allows different
ride heights to be either manually or automatically selected. By changing the
volume of air in each of the air springs, the system maintains ride height and
quality regardless of load.
Four height sensors monitor vehicle height - one for each wheel. Data
received from each sensor by the electronic control module is used to
maintain, add or release air in each spring by a series of solenoid valves.
Seven valves work together in a valve block to manage system heights and
air storage. An electric air compressor, regenerative air dryer, and a supply
reservoir are used to manage the air used in the system.
Range Rover Classic and New Range Rover use basically the same system,
differing only in a few details. 
						

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Table of Contents
INTRODUCTION.................................................................................................................2
TABLE OF CONTENTS......................................................................................................3
SYSTEM COMPONENTS...................................................................................................4
ELECTRONIC CONTROL UNIT (ECU).................................................................................4
BECM.................................................................................................................................4
RELAYS AND FUSES.........................................................................................................4
DISABLE SWITCH..............................................................................................................4
CONTROL SWITCHES........................................................................................................4
HEIGHT SENSORS.............................................................................................................5
AIR  COMPRESSOR............................................................................................................5
AIR  DRYER........................................................................................................................5
RESERVOIR.......................................................................................................................5
PRESSURE SWITCH..........................................................................................................6
VALVE BLOCK....................................................................................................................6
VALVE DRIVER..................................................................................................................6
AIR SPRINGS.....................................................................................................................7
NYLON AIR HARNESS........................................................................................................7
SYSTEM OPERATION.......................................................................................................8
SERVICE (RANGE ROVER CLASSIC)..............................................................................9
SYSTEM CALIBRATION....................................................................................................10
SUMMARY OF AVAILABLE FAULT MESSAGES................................................................10
ECU SELF DIAGNOSTIC LIMITATIONS.............................................................................11
FAULT MESSAGE DIAGNOSIS.........................................................................................12
SYMPTOM  DIAGNOSIS....................................................................................................13
SERVICE (NEW RANGE ROVER)...................................................................................14
SYSTEM CALIBRATION....................................................................................................14
SUMMARY OF AVAILABLE FAULT MESSAGES................................................................15
ECU SELF DIAGNOSTIC LIMITATIONS.............................................................................15
FAULT MESSAGE DIAGNOSIS.........................................................................................17
SYMPTOM  DIAGNOSIS....................................................................................................18
RANGE ROVER CLASSIC CONNECTOR DETAILS......................................................20
NEW RANGE ROVER CONNECTOR DETAILS.............................................................25
PNEUMATIC DIAGRAMS.................................................................................................28
EXPECTED HEIGHT SENSOR BIT COUNTS.................................................................32 
						

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SYSTEM COMPONENTS
ELECTRONIC CONTROL UNIT (ECU)
The ECU, located under the right front seat on Range Rover Classic and the left front seat
on New Range Rover, communicates with the vehicle through a 35-cavity connector. Serial
data is available to retrieve fault messages and view real time data using TestBook. The
ECU is very reliable due to input and output overload protection.
BECM
NEW RANGE ROVER ONLY
The BeCM provides basic inputs to the ECU, receives fault messages and controls the
message center.
RELAYS AND FUSES
RANGE  ROVER  CLASSIC
The system incorporates two fuses and three relays, all located under the right front seat. A
30-amp ‘maxifuse’ is used to limit current to the compressor and diaphragm solenoid. A 15-
amp fuse limits the ECU, valve driver, and pressure switch current. There is a four-pin
compressor relay, a five-pin warning lamp relay, and a five-pin turn-off relay. The turn-off
relay is used to maintain system power for approximately twenty seconds after the last door
is closed. The relay “wakes up” every six hours to level the vehicle down to the lowest
corner.
NEW RANGE ROVER
This system uses three fuses and one relay located in the under-hood fuse box. A four-pin
compressor relay and a 30-amp ‘maxifuse’ are used for the diaphragm solenoid and
compressor functions. A 10-amp fuse (F44) limits the ECU, valve driver and pressure switch
current. Fuse F24 supplies the key-on signal. A six-pin delay turn-off relay is located under
the left front seat. Power is maintained in the system for approximately one hundred seconds
after the ignition is turned off or thirty seconds after the last door or tailgate is closed. This
relay “wakes up” every few hours to level the system.
DISABLE SWITCH
RANGE  ROVER  CLASSIC ONLY
The disable switch is located on the back of the right front seat. This switch simulates a door
open input to disable height changes by the ECU. The vehicle will gradually drop due to air
leakage. For safety reasons, height changes are enabled at 35 mph.
CONTROL SWITCHES
RANGE  ROVER  CLASSIC
Two momentary contact switches and one latching switch are located on the driver’s side of
the dash. These switches are used to change ride position as well as indicate system status
with integral lamps.
NEW RANGE ROVER
The rocker switches are located in the upper center console and are used to indicate current
system status and make manual height changes. 
						

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HEIGHT SENSORS
The height sensors are chassis mounted potentiometers that are connected via a link to the
corresponding suspension member (e.g. trailing arm, radius rod). Each sensor modifies a
five-volt reference voltage to report the height information to the ECU. This information is
converted by the ECU to a digital format or “bits”. Height information is available through
TestBook as “bit counts”.
AIR COMPRESSOR
The electric air compressor has an internal thermal switch which protects the motor from
overheating by signaling the ECU if the temperature exceeds 120º C. To meet altitude and
pressure requirements the compressor has a compression ratio of 22:1.
RANGE  ROVER  CLASSIC
The compressor, valve block, valve driver, and air dryer are attached to the chassis under
the passenger’s seat. Because these components are located below the wade height of the
vehicle, the inlet filter is located in the right rear quarter panel.
NEW RANGE ROVER
The compressor, valve block, valve driver, and air dryer are located under the hood on the
left inner fender. A serviceable inlet filter is located on the compressor crankcase.
AIR DRYER
The air dryer is located between the compressor and the reservoir. A diaphragm valve
directs exhausting air through the dryer in the opposite direction, removing accumulated
moisture from the dryer and thereby ‘regenerating‘ the dryer. The mounting position of the
dryer on New Range Rover models is vertical, taking advantage of gravity, to better expel
moisture during the exhaust process.
RESERVOIR
 CAUTION: The later style reservoirs (for both New Range Rover and Classic) have
a different size drain plug. This will require an adapter when performing a pressure test on
a later style reservoir. Use the following when doing the pressure test:
• Early  style—LRT-60-001
• Later style—LRT-60-001 and LRT-60-006
RANGE  ROVER  CLASSIC
A ten-liter supply tank is attached to the chassis on the driver’s side. One nylon air line
serves as both inlet and outlet for the system. The reservoir should be depressurized and
the drain plug removed and inspected for moisture at 30,000-mile intervals. If moisture is
found, the dryer should be replaced. Two different reservoirs are specified depending on
VIN: up to VIN SA654292 use NTC9825; from VIN SA654293 and up use ANR3754.
NEW RANGE ROVER
A nine-liter supply tank is mounted to the chassis on the right side. As in the Classic, a single
nylon line serves as both inlet and outlet. The inspection interval is also 30,000 miles, with
dryer replacement required if moisture is encountered. As in the Classic, two reservoirs are
specified depending on VIN: up to VIN TA340460 use ANR3645; from VIN TA340461 and
up use ANR5135. 
						

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PRESSURE SWITCH
The pressure switch is located in the valve block on both New Range Rover and Classic with
the exception of Classic with a VIN up to SA654292. The pressure switch on these models is
located on the air reservoir. The pressure switch contacts should be open at pressures
below 7.6 BAR (110 psi). The pressure switch contacts should be closed at a pressure of
10.1 BAR (154. Psi) A deviation of ±0.4 BAR (56 psi) is allowable for all pressure
measurements.
VALVE BLOCK
The valve block controls the flow of air in the system in response to decisions made by the
ECU. This is accomplished through the use of solenoids, one-way check valves and a
fabricated block or manifold. Six “hit and drop” solenoids (explained below) are used, one for
each corner and one each for inlet and exhaust. One direct acting diaphragm solenoid is
used to control the direction of airflow in the dryer and is energized by the compressor relay.
A blow-off valve is located on the valve block in the event the system pressure exceeds
12.5 BAR (180 psi).
VALVE DRIVER
The six solenoid valves are relatively large because of the response time required by the
system. If these solenoid valves were operated for long periods of time under conditions of
high temperature or high currents, they would overheat and fail. To prevent this, the valve
driver controls the amount of current that flows through each solenoid coil. Because the
current required to open the solenoid is considerably higher than the current required to hold
the solenoid open, a “hit and drop” signal is used. Upon a valve open request the control
voltage is near 0V for 0.050 seconds (50 milliseconds) then is pulsed to limit current through
the coil. The pulsed voltage will read approximately 9 volts with a high impedance DVOM or
can be viewed with an oscilloscope to be a 24 KHz 12-volt square waveform. The steady
state current passing through each coil is approximately 1 amp. 
						

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AIR SPRINGS
The air springs are mounted in the same position as the conventional coil springs. The air
spring unit consists of a top plate, a rubber diaphragm, and a lower piston. Front and rear air
springs are not interchangeable. Upon failure the entire unit must be replaced.
NYLON AIR HARNESS
All pneumatic components are connected by nylon air lines to maximize corrosion resistance
and minimize fatigue failures. Each air spring and the reservoir are connected by a 6mm
pipe which is repairable using part number STC8580. 
						

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SYSTEM OPERATION
DOOR OPEN “WAKE-UP”
The system “wakes up” as soon as any door is opened. After all doors are closed, system
leveling could take place if any height sensors actual value differs from its target value by
more than ± 2 bits. The target value is determined by the lowest sensor input. If all the doors
are then closed, the delay relay will time out in twenty seconds. Height changes are inhibited
when any door (or tailgate on NRR) is open, up to a speed of 35 mph.
ENGINE RUNNING “WAKE-UP”
When the ignition key is turned to position II, the ECU wakes up again and another leveling
could be required. On New Range Rover all warning lights are illuminated to indicate power
without ECU activity, on Classic the lights illuminate at engine start. The system becomes
active when the engine is started and the ECU receives an rpm signal greater than 500 rpm.
The ECU will close the compressor relay and attempt to pressurize the reservoir. This
attempt will take place if the pressure switch is open, the thermal switch is closed and the
system is not trying to exhaust any air. Remember that air cannot enter and leave the
system at the same time.
IN GEAR HEIGHT REQUEST
When the transmission is moved out of Park, the system will request Standard ride height.
The ride height lamp will flash during this process. The compressor operation will be stopped
if the vehicle exceeds 1 mph to allow the front axle to level. The leveling operation opens
both front corner valves for only three seconds to allow pressures to equalize between the
front air springs. This will be repeated every time the vehicle speed drops to zero. In stop-
and-go traffic a lot of extra valve activity may be heard.
BRAKE SWITCH INFLUENCE
Brake switch input will interrupt the standard ride height request for three minutes (one
minute on Classic). However, if the vehicle is travelling at 1 to 5 mph, the ride height change
will be allowed in spite of the brake switch signal.
COMPRESSOR OPERATION
The compressor will continue to operate if the pressure switch remains open. If the
compressor should become overheated, the thermal switch will open a path to ground and
the ECU will shut the compressor down for a three-minute cool-down period. After three
minutes have elapsed, the ECU will re-energize the circuit. If the thermal switch still has an
open path to ground, another three-minute cool-down period will take place. This will
continue until the path to ground is closed in the thermal switch indicating the cool-down has
been successful. Once the cool-down is successful, the compressor will again operate.
AUTOMATIC HEIGHT SELECTION
The system will default to extended ride height if the system is unable to lower a sensor’s bit
count for any ten-second period, indicating the vehicle is “high centered”. A flashing high
profile lamp will indicate extended ride height. The system will stay in this mode for ten
minutes or until the operator manually requests a lower ride height. The system could also
drop to standard if the vehicle speed exceeds 35 mph.
The system will automatically drop to low profile when the vehicle speed exceeds 50 mph for
more than thirty seconds. The lower lamp will be illuminated. This automatic feature should
be cancelled while towing by depressing the standard height button. This feature can be
selected at any speed on Range Rover by pressing the inhibit switch and the down rocker
switch. 
						

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SERVICE (RANGE ROVER CLASSIC)
The most useful tool available to repair any EAS problem is TestBook. The system is only
trying to make four sensors stay within a defined error range. Each rear sensor individually
should be within 2 bits of its target value while the front sensor values are averaged. See
TIB 60/02/94/US
The TestBook menu offers the following utilities:
CALIBRATE–This routine should only be performed when a height sensor or ECU has been
replaced.
DEFLATE–Used to depressurize the system; this function will not work if the inlet or exhaust
solenoids have failed.
DYNAMIC TESTS–Provides real-time serial data for each subroutine.
• Heights and Valves–Height sensor data.
• Switches–All input switch data.
• Compressor and Speeds–Input and output data
SYSTEM TEST–Read faults, performs complete system functionality test including pressure
switch
VALVE CYCLING–Used to manually open valves and run the compressor.
The current CD does not provide selection for 93 and 94 model year. This is because the
first three questions under System Test make reference to a lamp in the instrument pack that
doesn’t exist for these model years. To access this utility, use the following procedure:
TestBook  screen  1:
Ensure ignition is OFF.
Does Air Suspension warning lamp in instrument pack illuminate?
Answer: NO.
TestBook  screen  2:
Ensure inhibit switch is not depressed. Turn ignition to position 2. Do not start engine.
Does Air Suspension lamp illuminate?
Answer: NO.
TestBook  screen  3:
Disconnect Black diagnostic connector.
Does Air Suspension warning lamp illuminate?
Answer: YES.
You will then be prompted to initialize the ECU. If further problems are experienced, refer to
page 12 of this document to locate the problem. 
						

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RANGE  ROVER  CLASSIC  SERVICE  cont.
SYSTEM CALIBRATION
In an effort to adjust for variations between sensors and their locations on the chassis, it is
necessary to calibrate the vehicle’s body to specific sensor bit counts. This is accomplished
by supplying height measurements to specific height sensor outputs. At the start of the
routine, all existing sensor target values are over-written with new default values. This way a
consistent starting point is used with all vehicles.
During the calibration routine both the pressure switch and the thermal switch are ignored.
The routine should be completed as quickly as possible in order to avoid potential
compressor damage. If the first attempt fails, your new calibration data points become those
calculated by the ECU during the first attempt. This enables further “tuning” to reach the final
goal of 790 ± 7mm at Standard Ride Height (See TIB 60/02/94/US).
SUMMARY OF AVAILABLE FAULT MESSAGES
FRONT LEFT SENSOR ABOVE LIMITFRONT LEFT SENSOR BELOW LIMIT
FRONT RIGHT SENSOR ABOVE LIMITFRONT RIGHT SENSOR BELOW LIMIT
REAR LEFT SENSOR ABOVE LIMITREAR LEFT SENSOR BELOW LIMIT
REAR RIGHT SENSOR ABOVE LIMITREAR RIGHT SENSOR BELOW LIMIT
ENGINE SPEEDVEHICLE SPEED
PRESSURE SWITCH STUCK ONPRESSURE SWITCH STUCK OFF
COMPRESSOR FAILUREAIR SUPPLY LEAK
CANNOT LOWER FRONT LEFTCANNOT LOWER FRONT RIGHT
CANNOT LOWER REAR LEFTCANNOT LOWER REAR RIGHT
FRONT LEFT VALVE STUCK OPENFRONT RIGHT VALVE STUCK OPEN
REAR RIGHT VALVE STUCK OPENREAR LEFT VALVE STUCK OPEN
INLET VALVE STUCK OPENEXHAUST VALVE STUCK OPEN
FRONT LEFT VALVE STUCK CLOSEDFRONT RIGHT VALVE STUCK CLOSED
REAR LEFT VALVE STUCK CLOSEDREAR RIGHT VALVE STUCK CLOSED
INLET VALVE STUCK CLOSEDEXHAUST VALVE STUCK CLOSED