Diagnostics and Maintenance
When vehicles are set to transportation mode the air suspension system adopts different functionality to optimize the rear suspension height for loading and off-loading clearances. The vehicle can be switched in and out of transportation mode using Jaguar approved diagnostic equipment. In transportation mode, the rear suspension height is set to 25 mm (1 in.) above the nominal design height. If the suspension height is lower than the transportation mode set point, the message Vehicle Too Low is also displayed in the message center. When the correct height is reached (engine running) the Vehicle Too Low message is switched off.
The air suspension system has a number of special modes that may be used during vehicle servicing or repair. These modes can disable the air suspension system, make it operate within tighter tolerances or deflate the air springs and/or air reservoir. While one of these modes is active the message Air Suspension Not in Customer Mode is displayed in the IC. The air suspension system is set in and out of these modes using Jaguar approved diagnostic equipment.
Tight Tolerance Mode can be set manually.
If a fault occurs in the air suspension system, a related DTC (Diagnostic Trouble Code) is stored in the ISCM. The ISCM adopts a default leveling strategy which is most appropriate for the fault and vehicle safety. This reduces the functionality of the air suspension system depending on the type and severity of fault. A message is displayed, and an amber or red warning indicator is illuminated, in the IC. A warning chime may sound when the fault message is displayed.
The following table lists the air suspension system warning indicators, messages and chimes:
| TRIANGLE WARNING INDICATOR | MESSAGE | CHIME | FAULT | ACTION |
|---|---|---|---|---|
| Amber | Suspension Fault | Alert chime when message first displayed | Fault detected that may result in some reduction in system performance or refinement | Rectify fault |
| Amber | Vehicle Too Low | Vehicle in transportation mode: Information chime repeated while vehicle is too low; chime stops when transportation height achieved | Vehicle rear too low when loading. Displayed when vehicle at rest if too low | Wait until vehicle has risen before driving |
| Amber | Vehicle Too Low | Vehicle not in transportation mode: No chime | The rear suspension is more than 50 mm (2 in.) below nominal height and the vehicle is at rest | Wait until vehicle has risen before driving |
| Red | Vehicle Too Low | Vehicle in transportation mode: Information chime repeated while vehicle is too low; chime stops when loading height achieved | Vehicle rear too low when loading and vehicle is moving | Stop until vehicle has risen |
| Red | Vehicle Too Low | Vehicle not in transportation mode: No chime | The rear suspension is more than 50 mm (2 in.) below nominal height and the vehicle is moving. | Stop or proceed cautiously until vehicle has risen |
| Amber | Air Suspension Not In Customer Mode | No chime | Air suspension system is in special mode used for vehicle servicing or repair | Change to customer mode with Jaguar approved diagnostic equipment |
The following system fault will not necessarily cause a DTC to be set:
| SYMPTOM | POSSIBLE CAUSE |
|---|---|
| Vehicle leans/tilts after being left overnight or for some days | Leak from air spring, air spring valve or their pipe connections |
Calibration or height setting is the process of adjusting the values stored in the ISCM for the suspension height sensor offsets for each of the four corners. Each of the suspension height sensors measures the position of the associated wheel with respect to the vehicle chassis and generates a corresponding voltage signal. Each of these voltage signals is read by the module and converted to a height value in millimeters. Ideally this height value would exactly match the actual value for each wheel, however, due to build and component tolerances there can be an offset between these two sets of values.
The calibration process sets the necessary value for this offset for each suspension height sensor so that the actual and calculated values are equal. System calibration is required in the following cases:
- A suspension height sensor is removed or replaced.
- A replacement ISCM is fitted.
- If any part to which the height sensor is mechanically connected is dismantled and re-built.
The calibration procedure is carried out using Jaguar approved diagnostic equipment and a suspension height measurement tool.
The ISCM contains a self test function, that can be activated by Jaguar approved diagnostic equipment. The test is primarily an electrical test. Checks for stuck valves or leaking valves etc. are not included.
The test routine activates each output (valves and compressor) in turn, and monitors electrical connections. The routine takes approximately 30 seconds to complete, but may be terminated immediately by switching the ignition off. Operation of the valves during this test may cause small quantities of air flow into or out of the air springs. As a result the vehicle may make small changes in height.
The self test operates in the following sequence:
- Opens exhaust valve 100%, then closes valve.
- Turns air compressor on and off.
- Opens rear left air spring valve 100%, then closes valve.
- Opens rear right air spring valve 100%, then closes valve.
- Opens the air reservoir valve 100% for 2 seconds, then closes valve.
To de-pressurize the system air is vented through the valve block, the air compressor assembly (which regenerates the Air suspension air drier), the filter and the Air suspension silencer to atmosphere. The system is pressurized using the air compressor assembly. The de-pressurization and pressurization of the air suspension system is initiated using Jaguar approved diagnostic equipment.