Operation Principle

WARNING: This page is about a different car, the 2013 Infiniti M56 and 2013 Infiniti M37. However, it is still accessible from the selected car via links, so may be relevant.

When turning the steering wheel to the right.

During Parking

Fig 1: EPS System Operation Diagram (During Parking)

Courtesy of NISSAN NORTH AMERICA, INC.

Power steering solenoid valve is closed while a vehicle is stopped.
Pinion "1R", "2R" and "3R" are closed depending on steering torque of steering wheel.
Oil pressure "P" in the gear housing assembly is the sum of oil pressures occurring in "2R" and "3R". This results in a light steering force because of high pressure.

During High-speed Operation

Fig 2: EPS System Operation Diagram (During High-Speed)

Courtesy of NISSAN NORTH AMERICA, INC.

Power steering solenoid valve is opened during high-speed operation.
Pinion "1R", "2R" and "3R" are closed depending on steering torque of steering wheel.
"2R" is bypassed to the return port by the EPS solenoid valve.
Oil pressure "P" in the gear housing assembly includes only oil pressure occurring in "3R" and results in a heavy steering force.