RRSTDV8
Member Since: 12 Aug 2011
Location: Northamptonshire
Posts: 8980
 
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Cross articulation fault should give a red light and suspension on the bump stops. It happened to me a week ago. Mine appears to have been a calibration corruption - I'd been trying to diagnose a strange ride height issue and had been "playing" 
Flicked through the manual and found this:
Quote: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 onsignal behaviour, 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 suitablecompressor 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 modeheight 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 modeheight 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 isbelow 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 bein
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 atthe '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 closedat 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 inthe 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 isable 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.
2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed
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Wed Apr 23 2014 11:42pm |
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with the arrows over the top ? Do you get any error - warning messages ?
