Air Suspension System Operation

The Chassis Control Module (CHCM) adjusts the quantity of air in the springs to maintain the rear suspension at the required height. The CHCM calculates a target height for the rear suspension based on the average height of the front suspension. If the actual height of the rear suspension is outside the tolerance band for the target height, for a given length of time, the CHCM then adjusts the actual height to the target height.

The normal tolerance band is ±9 mm (0.35 in.).

This changes to ±3 mm (0.12 in.) when:

• The vehicle is parked for 15 minutes with the engine running and all doors closed.
• Putting the CHCM into a special mode using the Jaguar Land Rover approved diagnostic equipment.

The tight tolerance band will also be activated by the following procedures:

1. All doors closed and the engine is running.
2. Open the driver's door.
3. Tap brake pedal lightly 3 times, enough to make sure that the brake lights turn on and off 3 times.
4. Close the driver's door within 10 seconds of the first pedal tap.
5. The Instrument Cluster (IC) will chime twice around 1 second after the driver's door is closed to confirm that the process has been successful.

The IC will chime twice each subsequent time the driver's door is closed while the air suspension remains in this tight tolerance mode.

To exit this state turn off the ignition or exceed 8kmh (5mph).

To decrease suspension height, the CHCM opens the exhaust valve in the air compressor assembly and the air spring valves in the valve block. The exhaust valve and the air spring valves release air from the air springs. To raise the suspension height, the module opens the air spring valves to introduce air into the air springs using air from the air compressor.