ECU Inputs

The air suspension system is controlled by ECU, which operates dependent on driver selected inputs plus those listed below. In each mode, ECU maintains requested ride height by adjusting volume of air in one or more air springs.

• Battery
  
  12 volt supply from ignition load relay.
• Engine
  
  From A/C generator phase tap, signals engine speed to ECU. Note that engine must be running for all height changes, except access and self-levelling when parked. The compressor will be disabled if engine speed falls below 500 RPM. This is to prevent compressor drawing current from battery when A/C generator is not changing.
• Height Sensors
  
  4 potentiometer height sensors provide suspension height signals to ECU.
• Road Speed
  
  Vehicle speed sensor provides information enabling height changes to occur at correct road speed. Input speed signal to ECU is from a buffer unit located in driver's side footwell.
• Interior Light Delay Unit
  
  Signals ECU if any door, not tailgate, is opened, which immediately suspends all height changes.
• Parking Brake Switch (M/T)
  
  Parking brake must be ON to enter ACCESS.
• Gearbox Inhibit Switch (A/T)
  
  Transmission must be in park to enter ACCESS, parking brake on or off.
• Foot Brake Switch (Brake Light)
  
  When foot brake is applied, and for one second after it is released, all height levelling is suspended below one MPH (1.6 kph) and above 5 MPH (8 kph). The purpose of this is to prevent system reacting to suspension movement caused by weight transfer during braking and to prevent suspension wind up during height change. Note that this inhibit function is removed after 60 seconds; e.g., if foot brake is held on for this time.
• Delayed Turn Off Relay
  
  Remains energized after switching engine off and exiting vehicle, enables self levelling to occur for 20 seconds. If vehicle is stationary, ECU will energize relay every six hours to allow self levelling to occur if necessary.
• Reservoir Pressure Switch
  
  When ECU detects an output from pressure switch indicating low pressure, ECU will operate compressor relay until pressure switch indicates normal pressure.
• Diagnostic Plug Ground
  
  Note that two halves of diagnostic plug are normally connected. When disconnected, system will not operate. It will remain frozen at its current height until reconnected.
• Disable Switch
  
  In disable position, switch sends a door open signal to ECU. This freezes system in position at speeds below 35 MPH (56 kph).