HICAS (High Capacity Actively Controlled Suspension) is Nissan's rear wheel steering system found on cars ranging from the more recent Skyline and Z iterations to smaller models like the 240SX/180SX. It is also found on models from Nissan's Infiniti division, such as the Q45 and the M45/M35. Unlike other four wheel steering systems, HICAS and Super HICAS is fitted to improve handling rather than as a parking aid.
Earlier HICAS versions used hydraulics to steer the rear wheels. The hydraulic system was powered by the power steering pump and used speed sensors to determine how much and which direction to steer the rear wheels. Later versions, called Super HICAS, moved to an electric actuator for the rear steering rack, making the system much lighter. The Super HICAS system also used its own computer to control the system insted of speed sensors. HICAS and Super HICAS rear wheel steering is limited to about 1 degree in either direction.
HICAS was introduced on the 1986 Skyline GTS coupes (GTS, GTS-R, and GTS-X). The system was later adaped to work on many models in the Nissan range, beginning with the Passage GT.