Jaguar XJ (X350). Manual — part 109

A pressure retaining valve (PRV) is located in each air spring which retains sufficient pressure to

protect the air spring membrane during service and handling.

NOTE:

De-pressurization and re-pressurization of the air suspension system should be performed using

the Jaguar approved diagnostic system prior to, and after, any work being carried out.

Solenoid Valve Block

The solenoid valve block contains five individual solenoid valves (one per air spring and one for the

vehicle reservoir). A pressure sensor is incorporated into the solenoid valve block and monitors air

spring and reservoir pressure. The solenoid valve block is mounted on isolators to reduce valve

operation noise. Pipe connections are provided for the front and rear air spring assemblies and also

the reservoir and compressor. The compressor to valve block port and the rear air spring ports are 4

mm in diameter with the front air spring ports being 6 mm in diameter. Each of the solenoid valve

block ports and air pipes are color coded (pink, blue, white, yellow, red and brown) for correct

connection.

Reservoir

The reservoir has a volume of 4.5 liters with a maximum design pressure of 15 bar (218 psi).

Dependent on load conditions, this store of reserve air is sufficient for two full lifts. The system

automatically replenishes the reservoir by way of the compressor.

Air Suspension Module

The air suspension module (ASM) is accessed from the right-hand side of the vehicle, behind the back

of the rear seat. The ASM can be recognized by the 4 individually colored connectors (gold, grey,

yellow and pink) and the 'WABCO' logo on the front of the module. ASM calibration is required when

either a replacement module is fitted, or if any height sensors have been removed/refitted or

replaced.

NOTE:

When installing a new air suspension module it will be necessary to configure the module into

the customer mode using the Jaguar approved diagnostic system.

Compressor

The air compressor is located in the left-hand front wheel arch behind the bumper beam assembly. It

contains an air filter, an integral regenerative air drier element plus an air exhaust solenoid valve.

The compressor is isolated from the main body structure by 3 mounts, each incorporating a rubber

bush and metal spring. The maximum pressure developed by the system is 15 bar (218 psi) with a

compressor pressure relief valve fitted, set to relieve pressures above 17 Bar (247 psi). The

compressor only operates whilst the engine is running. To guard against the compressor overheating

the ASM may shut down the compressor to allow cooling to take place. Re-activation of the

compressor depends on vehicle activity and is generally no longer than 120 seconds.

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Diagnosis and testing

Vehicle Dynamic Suspension

Operating modes

Before it will be possible to verify the customer concern, it will be necessary to understand the

modes of the system to establish what the system should and should not do in each mode. The table

below should help in understanding the operating modes.

Vehicle operating

condition

Air suspension

operating mode

Levelling status

Static, parked. No

occupant or loading

activity for 30 minutes

Sleep mode

•

Compressor unpowered

•

Only lowering allowed

Static, parked. Occupant

entry and/or loading

activity within past 30

minutes

Preliminary

mode

•

Lifting with reservoir

•

Lowering permitted

•

Compressor unpowered

Static, parked with engine

running

Stance mode

•

Lifting with reservoir

•

Lowering permitted

•

Compressor unpowered unless reservoir
pressure is below a preset minimum and the
vehicle is below the compressor activation
height

Driving

Drive mode

•

Lowering permitted at all speeds

When vehicle speed is below 40 km/h (25 mph):

•

Lifting with reservoir

•

Compressor unpowered unless reservoir
pressure is below a preset minimum and the
vehicle is below the compressor activation
height

When vehicle speed is above 40 km/h (25 mph):

•

Compressor powered to lift vehicle and refill
reservoir

TRANSPORTATION MODE

The vehicle will arrive at the dealership in transportation mode, and will need to be reset to

customer mode at PDI (this will be carried out by a Jaguar dealer).

Transportation mode keeps the vehicle in a raised condition to allow adequate clearance for

transporter loading and unloading. If the vehicle has lowered, the compressor is used to lift the

vehicle. Until a suitable height is reached, the message center will display Vehicle too low. The

message, Air Suspension Fault will be displayed on the message center at all times whilst the vehicle

is in transportation mode.

CUSTOMER MODE

The modes below are all enabled in this mode.

SLEEP MODE

The system shuts down into sleep mode 30 minutes after the vehicle is left, and "wakes up" to check

the ride height every 24 hours. If the vehicle is not level, the system lowers until the vehicle attitude

is correct. The system will not lift the vehicle while in sleep mode to conserve reservoir pressure and

battery power.

PRELIMINARY MODE

When a door or luggage compartment is opened, or the engine is switched off from a standstill

condition, (see below) this mode is enabled.

In Preliminary mode, the reservoir is used to lift the vehicle to level it to within a greater tolerance

than in stance or drive modes (see below).

STANCE MODE

When the vehicle is stationary with the engine running, (standstill condition) the vehicle will be

levelled to within a closer tolerance than in preliminary mode to ensure that the trim heights are

correct before moving off.

Any lifting necessary will be done from the reservoir, unless the vehicle is below a preset minimum

height and the reservoir pressure is below a preset minimum, in which case, the compressor be will

used to lift the vehicle.

DRIVE MODE

When the vehicle speed is above the preset threshold, the compressor is always used to lift the

vehicle. This threshold is also used to initiate recharging of the reservoir. The following functions are

enabled in drive mode;

Speed Lowering Function

To reduce aerodynamic drag and enhance vehicle stability, the system lowers the vehicle at high road

speeds.

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