Circuit Description
AIR SUSPENSION
OPERATION
Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fusible link 5 and fuse 57 of the passenger compartment fuse box (C0632) on an R wire. Fuse 57 (C0582) provides a constant battery feed to the air suspension ECU (C2030) on an RN wire. The air suspension ECU (C2030) is earthed on an N wire.
Fusible link 5 (C0588) is connected to fuse 18 of the rear fuse box (C2024) by an R wire. Fuse 18 provides a constant battery feed to the air suspension relay, which is also located in the rear fuse box.
Air Suspension ECU
The air suspension ECU (C0867) is located behind the LH side of the fascia, and is connected to the centre console rotary switch (C0700) as follows:
- If the rotary switch is turned to select a lower suspension setting, an earth path is created via the switch on a UP wire
- If the rotary switch is turned to select a higher suspension setting, an earth path is created via the switch on an SR wire
- If the 'Hold' switch has been selected, an earth path is created via the switch on a YW wire.
NOTE: The air suspension ECU will only allow the suspension settings to change if all the conditions described in the 'Suspension' of the System Description and Operation.
The air suspension ECU (C0867) also provides a feed to the LED'S contained on the face of the centre console rotary switch (C0700) as follows:
- To the 'Motorway' LED on an SY wire
- To the 'Off Road' LED on an SG wire
- To the 'Access' LED on an SP wire
- To the 'Standard' LED on a WY wire
- To the 'Hold' LED on an SU wire.
Height Sensors
The Air Suspension ECU monitors the height of the vehicle via four height sensors. The air suspension ECU is connected to the height sensors as follows:
RH Front Height Sensor
The air suspension ECU (C0867) provides a feed to the RH front height sensor (C1697) on a BW wire. An earth path is provided for the sensor on a BN wire. By measuring the voltage returned on a BS wire, the air suspension ECU can determine the height of the RH front of the vehicle.
LH Front Height Sensor
The air suspension ECU (C0867) provides a feed to the LH front height sensor (C1696) on an SB wire. An earth path is provided for the sensor on an SN wire. By measuring the voltage returned on an SW wire, the air suspension ECU can determine the height of the LH front of the vehicle.
RH Rear Height Sensor
The air suspension ECU (C0867) provides a feed to the RH rear height sensor (0698) on a YB wire. An earth path is provided for the sensor on a YN wire. By measuring the voltage returned on a YS wire, the air suspension ECU can determine the height of the RH rear of the vehicle.
LH Rear Height Sensor
The air suspension ECU (C0867) provides a feed to the LH rear height sensor (C1699) on a WB wire. An earth path is provided for the sensor on a WN wire. By measuring the voltage returned on a WS wire, the air suspension ECU can determine the height of the LH rear of the vehicle.
Cross Link Valves
The cross link valves connect the height sensors in pairs, front and rear. When air is required to flow between the two rear height sensors, the air suspension ECU (C2030) provides a feed to the rear cross link valve (C2033) on a UR wire. The air suspension ECU provides an earth path for the cross link valve on a UP wire.
When air is required to flow between the two front height sensors, the air suspension ECU (C2030) provides a feed to the front cross link valve (C2032) on a UN wire. The air suspension ECU provides an earth path for the cross link valve on a WU wire.
Air Supply Unit
The air supply unit is located in a sealed housing in the spare wheel well. Located within the unit is the compressor. To power the compressor, the air suspension ECU (C0867) provides a feed to the air suspension relay coil (C2022) on a B wire. The relay is located in the rear fuse box and is earthed (C2021) on an N wire. The energised relay (C2023) provides a battery feed from fuse 18 of the rear fuse box to the compressor (C0873) on an RY wire. The compressor (C0873) is earthed on an N wire.
The air suspension ECU (C0867) monitors the temperature within the air supply unit (C0873) by providing a feed to the temperature sensor on a BRY wire. The air suspension ECU determines the temperature within the air supply unit by measuring the voltage returned on an S wire.
Valve Block
The valve block contains five solenoid valves which control the air supply as follows:
RH Front
If air is required in the RH front air spring, the air suspension ECU (C0867) provides a feed to the valve block (C0770) on a UB wire. An earth path is provided by the ECU on a UY wire.
LH Front
If air is required in the LH front air spring, the air suspension ECU (C0867) provides a feed to the valve block (C0770) on a UB wire. An earth path is provided by the ECU on a US wire.
RH Rear
If air is required in the RH rear air spring, the air suspension ECU (C0867) provides a feed to the valve block (C0274) on a WP wire. An earth path is provided by the ECU on a WR wire.
LH Rear
If air is required in the LH rear air spring, the air suspension ECU (C0867) provides a feed to the valve block (C0274) on a WP wire. An earth path is provided by the ECU on a YP wire.
Reservoir Valve
The reservoir valve controls the air pressure supply from the reservoir to the air springs. The air suspension ECU (C0867) provides a feed to the valve block (C0771) on a UW wire, and an earth path on a UG wire.
Air Pressure Sensor
The air pressure sensor measures the pressure within the air reservoir. The air suspension ECU (C0867) provides a feed to the pressure sensor (C1611) on a Y wire. An earth path is provided for the sensor on a W wire. By measuring the voltage returned on a U wire, the air suspension ECU can determine the pressure within the air reservoir.