Part 2

Vehicle Dynamic Suspension

SPECIAL MODES

Door Open Functionality
If one or more of the vehicle doors are opened during a height change when the vehicle is stationary, the air suspension control module will restrict further height change. The door open signal is transmitted by the CJB on the high speed CAN bus and received by the air suspension control module. This keeps the vehicle level to the set height when a door opens to allow for changes in loading conditions.
A hardwired door status signal is also transmitted from the CJB to the air suspension control module. This signal provides door status information when the high speed CAN bus is off, i.e.; during periodic re-levelling.
The lamp on the air suspension switch for the target mode height will remain illuminated and the raising or lowering lamp will flash.
If all of the doors are closed within 90 seconds, the height change will resume. If the 90 second period is exceeded and all of the doors are not closed, the height change will be cancelled. The mode lamps showing the previously selected height and the target height will be illuminated. The mode height change can be reselected by operating the switch, however, if the vehicle is driven at speed of more than 5 mph (8 km/h) the control module will continue to raise or lower the vehicle to the target mode height.

Extended Mode
If the vehicle becomes grounded and the traction control becomes operational, the air suspension control module automatically increases the mass of air in the air springs to raise the vehicle clear of the obstruction. Extended mode is activated automatically and cannot be selected manually.
When the air suspension control module has activated the extended mode, the off-road mode lamp will flash if the suspension is above off-road mode height. The off-road mode and on-road mode lamps will flash if the suspension is between off-road mode and on-road mode heights. The on-road mode and access mode lamps will flash if the suspension is between on-road mode and access mode. A message will also be displayed in the message centre.
To exit the extended mode, press the air suspension switch briefly in the up or down position or alternatively drive the vehicle at a speed of more than 2 mph (3 km/h) for 45 seconds.

Additional Lift in Extended Mode
When extended mode has been invoked and the automatic lifting of the vehicle is complete, the driver can request an additional lift of the vehicle. This can be particularly useful when extended mode has been activated on soft surfaces.
The additional lift can be requested once the raising lamp has extinguished. Press and hold the air suspension switch in the up position for 3 seconds whilst simultaneously depressing the brake pedal. A chime from the instrument cluster will sound to confirm that the request has been accepted. The raising symbol will be illuminated while the vehicle is being lifted.

Suspension Prevented From Moving
If the air suspension control module is attempting to change the suspension height and it detects that the suspension is prevented from moving, the control module will stop all suspension movement. This can be caused by jacking the vehicle, attempting to lower the vehicle onto an object or raising the vehicle against an obstruction.
The air suspension switch lamps operate as described for extended mode and the same message is displayed in the message centre. To start the air suspension system operating, press the air suspension switch briefly in the up or down position or drive the vehicle at a speed of more than 12.5 mph (20 km/h).

Periodic Re-levelling
When the vehicle is parked, the air suspension control module 'wakes up' two hours after the ignition was last switched off and then once every six hours. The vehicle height is checked and if the vehicle is not level within a pre-set tolerance, small downwards height adjustments may be made automatically.

Transportation Mode
Transportation mode is a factory set mode which locks the suspension to enable the vehicle to be safely lashed to a transporter. Transportation mode can only be selected or deselected using a Land Rover approved diagnostic system.
When the ignition switch is switched off, the vehicle will be lowered onto the bump stops. This ensures that the securing straps do not become loose should air leak from the air springs.
When the engine is running, the air supply unit will operate to raise the vehicle height, allowing the vehicle to be loaded. When the ignition switch is subsequently switched off, the vehicle will again lower onto the bump stops. An audible warning will be emitted from the instrument cluster sounder until the vehicle has reached the higher transportation height.

AIR SUSPENSION CONTROL MODULE









The air suspension control module is located behind the instrument panel, on the driver's side 'A' pillar. The control module is attached to the 'A' pillar with a single screw and two plastic clips.
The air suspension control module also contains the software for the variable steering. For additional information, refer to Power Steering Power Steering

Calibration
A calibration routine is performed using a Land Rover approved diagnostic system to access the position of each corner of the vehicle and record the settings in the control module memory. Once set, the calibration is not required to be performed unless the air suspension control module is removed or replaced, a height sensor is removed or replaced or a suspension arm to which the sensor is connected is removed or replaced. If a removed height sensor is subsequently refitted, the calibration procedure will have to be performed to ensure the integrity of the system.
If the air supply unit, the reservoir, a valve block, a damper module or the air harness is removed or replaced, the system will not require recalibration.

Inputs and Outputs
The air suspension control module uses four harness connectors for all inputs and outputs.
The air suspension control module uses inputs received on the CAN bus from other vehicle systems. The system uses longitudinal acceleration, lateral acceleration, steering angle and wheel speed data to control the suspension operation in differing driving conditions.
The system will react differently if one or more of these data inputs is missing or incorrect, for example, if the steering angle sensor is missing or incorrect, the air suspension control module assumes a default value of zero which may result in some unnecessary levelling activity.

Steering - Servotronic Valve
The power steering Servotronic 2 system is controlled by software which is incorporated into the air suspension control module. The software responds to steering torque inputs and road speed signals and controls the assistance via a transducer valve located on the steering gear valve. The valve is connected by two wires to the control module on connector C2320. For details refer to the Power Steering section. For additional information, refer to Power Steering Power Steering

Air Supply Unit Relay
The air supply unit relay is located in the Battery Junction Box (BJB) in the engine compartment. The relay is connected directly to the battery via fusible link 10E (60A). The relay coil is connected to and controlled by the air suspension control module. The relay is used by the air suspension control module to control the operation of the compressor.
When air supply unit operation is required, the air suspension control module supplies power and ground for the relay coil which energizes, closing the relay contacts. This allows battery voltage via the fusible link to pass through the relay and operate the air supply unit electric motor and the compressor.
The battery voltage is also passed from the relay, via a splice joint in the harness, to the air suspension control module and is used as a signal that the relay is operating.

System Inhibits
A number of conditions exist where a change of ride height is undesirable. To counter this, the air suspension control module is programmed with a number of system inhibits. If any of the conditions detailed below exist, the air suspension control module will suspend height changes and height corrections.
Compressor
The temperature sensors located within the compressor protect the compressor from overheating. If the compressor temperature rises above set limits, the air suspension control module will inhibit the compressor operation. These limits are shown in the following table:









Cornering
If the air suspension control module registers a cornering force greater than 0.2g it will inhibit all height changes and corrections. The system will remain inhibited until the cornering force falls to less than 0.15g. The air suspension control module receives a message from the lateral acceleration sensor (which is an integral part of the ABS yaw rate sensor) on the high speed CAN bus for the cornering force.
Rapid Acceleration
If the air suspension control module registers a rapid acceleration greater than 0.2g it will inhibit all height changes and corrections. The system will remain inhibited until the rapid acceleration falls to less than 0.15g. Acceleration is calculated by the air suspension control module from a vehicle speed signal received via the high speed CAN bus.
Rapid Deceleration
If the air suspension control module registers a rapid deceleration smaller than -0.2g it will inhibit all height changes and corrections. The system will remain inhibited until the rapid deceleration rises above -0.15g. Deceleration is calculated by the air suspension control module from a vehicle speed signal received via the high speed CAN bus.
Vehicle Jack
The air suspension control module will inhibit all height changes and corrections if it detects a corner lowering too slowly for more than 1.2 seconds. This is interpreted as the corner identified as moving too slowly being supported on a jack. In this situation, the corner height will not change when air is released from the air spring because the jack acts as a mechanical prop. The system will remain inhibited until any of the following conditions exist:
- The air suspension switch is moved to the up or down position
- Vehicle speed rises to more than 2 mph (3 km/h) for more than 45 seconds.
Door Open
The air suspension control module will stop all height change requests while any of the doors are open. Vehicle levelling continues with a door open by keeping the vehicle at the height when the door was opened if the vehicle load changes.
Battery Voltage
If the supply voltage measured by the control module is less than 10 volts for more than 0.25 seconds or more than 17.5 volts for more than 0.25 seconds, all valve and compressor operation is suspended. Operation is resumed when the battery voltage is more than 11 volts or less than 16.5 volts. A diagnostic code is stored if the battery voltage is out of range after the engine has been running for more than 10 seconds.

Diagnostics
The air suspension control module can store fault codes which can be retrieved using a Land Rover approved diagnostic system. The diagnostic information is obtained via the diagnostic socket which is located in the lower instrument panel closing panel, on the driver's side, below the steering column.
The diagnostic socket allows the exchange of information between the various control modules on the bus systems and a Land Rover approved diagnostic system or a diagnostic tool. This allows the fast retrieval of diagnostic information and programming of certain functions using a Land Rover approved diagnostic system.
Fault Detection
The air suspension control module performs fault detection and plausibility checks. Fault detection is limited to faults that the control module can directly measure as follows:
- Sensor electrical hardware faults
- Valve electrical hardware faults
- Sensor and actuator supply faults
- Bus failures
- Control module hardware errors.
Plausibility checks are checks on signal behavior, as follows:
- Average height does not change correctly
- Height changes too slowly
- Gallery pressure
- Does not increase fast enough when reservoir filling requested
- Increases when system is inactive
- Too low when lifting is requested
- Increases too rapidly when filling reservoir
- Does not decrease when gallery is vented
- Pressure varies too much when inactive.
- Compressor temperature
- Sensor voltage too large - head and brush sensors (short circuit to battery)
- Takes too long to be readable after suitable compressor run time - head and brush sensors
- Does not increase when compressor active - head sensor only
- Sensor activity
- Signal floating
- Constant articulation when moving
When a fault is detected, the air suspension control module will attempt to maintain a comfortable ride quality and where possible will retain as much functionality as possible.
The system functionality depends on the severity of the fault.
Faults
- Height sensor faults (hardware faults) and reservoir valve block failure
- Retain full functionality with no 'refinements', e.g. cross-link valves inoperative, no compensation for uneven surfaces.
- Pressure sensor faults, compressor faults, corner valves stuck shut
- Vehicle returns to on-road mode height when next requested
- Levels at 'current' height.
- Reservoir valve stuck open, exhaust valve stuck shut if below on-road mode height, corner valves stuck open if above on-road mode height
- Vehicle returns to on-road mode height when next requested
- Does not level at 'current' height.
- Failure of multiple height sensors, cross-articulation when driving, calibration corrupted
- Vehicle lowers to bump stops.
- ABS module failure, CAN bus failure
- If the air suspension control module loses communications with the ABS module or the ABS module reports a fault, the air suspension control module immediately returns to the 'default' height, which is below the on-road ride height. Once at the default height, the control module will continue to level the vehicle at this height. It is unlikely that the fault will be in the air suspension control module. When the fault is repaired, the air suspension control module will resume full functionality but the error will remain in the control module memory.
For major faults the control module will not level the vehicle at the 'current' ride height. The control module freezes height changes until it receives a manual or automatic request for height change. The control module will return to standard height if possible and freezes once standard height is achieved.
If the suspension is above the on-road height and the air suspension control module cannot lower the suspension, all height changes will be frozen. The control module will issue a message on the high speed CAN bus which is received by the instrument cluster which displays a maximum advisable speed in the message centre. An immediate 'freeze' of the vehicle height is caused by the following:
- Failure of more than one height sensor - vehicle on bump stops
- Implausible articulation symptoms detected - vehicle on bump stops
- Valve or solenoid failure - corner valve stuck open below on-road mode height or exhaust valve stuck shut above on-road mode height
- Stuck corner or whole vehicle (diagnosed using plausibility of the sensor inputs).
If height change is not possible, e.g. exhaust valve failed closed at off-road height or compressor failed at access height, the control module will not level or change height.
If the air suspension control module has a hardware fault, the control module will disable all air suspension functions. Detectable hardware errors include memory error, control module failure and calibration errors.
Fault Messages
The air suspension has two methods which it can use to inform the driver of a fault in the air suspension system; the air suspension switch LED's and the instrument cluster message centre.
When minor faults occur and the air suspension control module is able to level the vehicle to the 'current' ride height, the air suspension switch LED's will display the current ride height.
If the air suspension control module suffers a major failure and there is no air suspension control, all the control switch LED's will remain off.
If a fault occurs and the air suspension control module can determine the ride height and the vehicle is above on-road mode height, the driver will be notified via a 'AIR SUSPENSION FAULT MAX SPEED 30 MPH (50 KM/H)' message in the message centre.
If the control module cannot determine the height of the vehicle, or the vehicle is not above on-road mode height, cannot be lowered and the vehicle speed is too high, an air suspension fault message is displayed.
If the vehicle is restricted to on-road mode height an air suspension fault normal height only message is displayed.