I had the same problem on my 89 GTS-T, first check your power steering reservoir, low fluid will throw a light. Also check for fluid leaks along the P/S lines and tighten any clamps you come across. Second, does it have an aftermarket steering wheel? If so, the problem sometimes is the sensor in the steering hub doesn’t “sense” that the wheel is centered and can’t adjust the HICAS so it shuts it down and locks it in place, causing your Skyline to “crabwalk” or look like its got a bent chassis rolling down the road. My problem wound up being several loose clamps and a few leaks draining the system. After tightening everything up and topping up my fluid, the light never came back on. Hope this helps, I know it’s only a start but it’s the easiest. Check some of the Skyline forums, they will have more info there.