| I have been having an intermittent power steering problem for a while. Every time I think I have fixed it it comes back. Very hard steering. Because it was so intermittent I was convinced it was one of the common electrical issues that is common for this type of problem, speed sensor, gauge cluster, power steering control unit ect. The other day it came back with full force. Now In order to turn the steering wheel you need arms the size of Spee's. My gut feeling has always told me it was probably the power steering pump but somehow I convinced myself that since it was so intermittent it was probably an electrical issue. Since I really hate having to replace the power steering pump I decided to try to rule out any electrical possibilities first. I had changed the gauge cluster so I put my old one back in. No change. I had already replaced the speed sensor but wait, the car's not moving. There should be no signal needed from the speed sensor in this case. I opened up my 90' FSM to find it only seemed to have troubleshooting procedures for an NA speed control unit. My 91' FSM did have troubleshooting for the HICAS/Speed control unit but the color codes for the wires were off. There are a few signals that go to the speed control unit that will cause the hard steering problem. Here is a picture of the HICAS/Speed control unit.
 I started checking the different signals going to the HICAS/Speed control unit which was becoming a PITA. One thing I could not obtain was getting the "ON" signal for the power steering switch. I was using my MDM-100 to show me that signal. I remember talking to someone once who told me they had a hard steering problem that turned out to be a lost signal from the steering angle sensor behind the steering wheel. This is one of the signals that goes to the HICAS/Speed control unit. From what little I was able to turn the steering wheel I was getting no "ON" signal from turning the steering wheel. With that I decided to check the steering angle sensor.
 All the signals checked out so here is some info on how this works. Like I previously showed in my CAS repair write-up, the speed angle sensor also uses photo sensors and a slotted disc. Here is a picture of the back side (side farthest from the steering wheel) of the steering angle sensor. The tiny slotted holes send a pulsed signal while the steering wheel is being turned.
 In this picture I have turned the disc slightly to show the one larger slotted hole. When positioned away from center this slot causes the steering angle sensor to send a constant five volt signal on one of the wires coming from it. It lets the HICAS/Speed control unit know that the wheel is turned from neutral.
 The piece attached to it with the two small screws contains the electronics and photo sensors.
 Some pictures of it unscrewed from the main unit.
 
On one side there is a removable cover.
 Cover removed. Yours may look a little different because I resoldered all the solder connection on mine. Bad solder connections are inherent on many of the circuit boards in our aging cars.
 The circuit board out.
 There are a total of four photo sensors or LEDs. Two transmitters and two receivers. When in place the disc spins between them.
 
During my troubleshooting I was turning the steering angle sensor while holding it in my hand. I was trying to get the power steering "ON" signal with my MDM-100 this way. No matter what I did I could not get the signal. After a day of troubleshooting I called it quits for the night. The next day I decided to use my other car and make comparisons back and forth. I first started comparing signals going to the HICAS/Speed control unit which all seemed OK. I was being baffled that even though all signals going to it were the same, why was I not getting the "ON" signal with to my MDM-100. Where was the signal coming from? Then I smacked myself in the head and said, wait a minute, I'm thinking about this all wrong. I was thinking that the signal was going to the power steering switch, not coming from it. So in my good car I pulled both connectors going to the HICAS/Speed control unit. The steering wheel was much harder to turn now but not nearly as hard as it was on my bad car. With both plugs disconnected I was still getting the "ON" signal when I turned my steering wheel. I smacked my head again! Of course I will not get the "ON" signal by just turning the steering angle sensor while holding it in my hand. You need to turn the steering wheel itself. I went back to my bad car and placed jumper wires from a multimeter to the two wires going to the power steering switch. I was getting the proper voltage, roughly 8.6 volts. When I tried to turn the wheel nothing changed on the voltage. You should see a drop to zero volts according to the FSM. Looking at the troubleshooting section for the power steering switch it referred to a component check on a different page if the condition was not obtained. Here is a picture from that page. What you see here is the only info given for how to check the switch.
 I checked the switch as stated and had an open condition. First thing I said was hey, maybe this is the problem. I was a little relieved because I had another line which had the switch in my parts car. I went out to my parts car and was anxious to see what a good reading would be. Using my multimeter I checked the switch and again it was open. I said wait a minute, two bad switches? I looked at the FSM again to confirm what I should be seeing. Then I realized that hey, this is a normally open switch. In order to read it as in the FSM you would have to have a working system and be turning the steering wheel allowing fluid to flow through the line in order to close the switch. As you can see, the FSM does not say anything about that in doing the component check. Anyway, here is where I am now. I'm still working on the problem, going now with my gut feeling as I should have in the beginning. At least I leaned a few things along the way. A few pics.
 
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Power steering woes. - 
