'91 Turbo.
I know there are plenty of thread about this, but the problem seems to be slightly different in my case.
The power steering hardly ever work, and while the flicking the ignition on/off a few times before starting sometimes seems to make it work, it never works for more than a few minutes, at most.
When I turn the accessories on, I can hear the P/S pump being on and making lots of noise.
We tried to replace the P/S relay with another one and that didn't do anything. We also tried to bypass the relay altogether, and that still didn't do anything. So it seems like the relay might not be the issue after all (note: the P/S light doesn't come on on the dash)
 
Since the P/S pump seems to be working (even when it shouldn't be), it seems like the only other cause would be a faulty P/S ECU?
Or is there something else that could be causing this? (I want to be sure cause the P/S ECUs aren't super cheap (if you are selling a cheap one that's working, PM me :) ))

I don't think I've ever heard of a power steer ecu going bad in the 15 or so years I've had mr2s. You should be able to buy one of those ecus cheap from one of the guys on this forum wrecking sw20s since they are not in demand.
The symptoms you are describing do sound like the common relay problem though. A member on hear wrote a bit of a guide about replacing the factory relay with an aftermarket solid state one for not much monies. Maybe check that out as well?
 

You say the power steering hardly ever works, is this observation from "feel" or have you tested it.  You mention that you can hear the PS pump on, and making a lot of noise.  Is this extra noise a recent event, or has it always been at this level.  Also, you've advised that the PS light does not come on.  This should light up when the ignition is turned to ON, then extinguish after 2 seconds.
 
First step to diagnosing this would be to make sure the light is working - if it doesn't in fact come on at turn on, check the bulb in the dash.  (Yes, I know, removing the dashboard is a PITA).  If it IS working (and it was just overlooked) there is a PS fault code procedure available.  Are you familiar with the method of "jumping" the data link connector terminals?  Codes you'll be looking for are likely to be 22 - "Excessive Current being supplied to PS Pump", and 31 "Worn PS Pump motor bushes"
 
I've only once heard of a PS ECU being faulty - but that car had had a serious electrical issue, and every controller had suffered from the voltage spikes!
 
Good luck with diagnosis, keep us updated with your progress . . .

dennis the menace
You say the power steering hardly ever works, is this observation from "feel" or have you tested it.  You mention that you can hear the PS pump on, and making a lot of noise.  Is this extra noise a recent event, or has it always been at this level.  Also, you've advised that the PS light does not come on.  This should light up when the ignition is turned to ON, then extinguish after 2 seconds.

 
Well, when the P/S is not working, the car is very hard to steer; while when it's actually working, the steering is quite light.
Re: the noise: I am not sure, I only bought that car recently, and it's always been noisy like that. For what I understand the P/S pump shouldn't be working (and making noise) while the car is not moving/ no steering input is given which is why we thought the problem was with the ECU not knowing when to turn the P/S on and off. Isn't that correct?
I could make a video if that would be of any help.
 

dennis the menace
First step to diagnosing this would be to make sure the light is working - if it doesn't in fact come on at turn on, check the bulb in the dash.  (Yes, I know, removing the dashboard is a PITA).  If it IS working (and it was just overlooked) there is a PS fault code procedure available.  Are you familiar with the method of "jumping" the data link connector terminals?  Codes you'll be looking for are likely to be 22 - "Excessive Current being supplied to PS Pump", and 31 "Worn PS Pump motor bushes"

 
Yes, you are right, the P/S light does come on for 2secs when turning the accessories on, and then disappear; but regardless if the P/S is working or not, the light never comes on after that.
We did try to pull some codes, but nothing came out.
 

dennis the menace
I've only once heard of a PS ECU being faulty - but that car had had a serious electrical issue, and every controller had suffered from the voltage spikes!
 
Good luck with diagnosis, keep us updated with your progress . . .

 
Also we did bypass the relay like this:
http://www.mr2oc.co.uk/kn...2-mk2.html?kbartid=112
and that didn't do anything.
 
Thanks for the replies.
 

do you have that position sensor thing on your steering wheel/indicator stalk?
 
also i had a small leak in one of the hoses for the power steering,when the oil level was normal the steering worked fine.as the oil leaked out it got harder to steer and the pump got louder...

 
 

Not sure if I do. There is a boss kit/ aftermarket steering wheel there, but I will check to see if I can see anything. But if the position sensor wasn't there, it would never work, wouldn't it?
 
I had a quick look last time, and I couldn't see a leak (everything was dry and no spots on the floor where I park it); also the P/S fluid level is full.

alexv
But if the position sensor wasn't there, it would never work, wouldn't it?
 

pretty much.power steering system would start up,but turn off after a minute or so.the power steering ecu controls a power steering driver.the driver supplys voltage to the pump.at low speed cornering it gives lots of voltage to move the pump faster.at high speed cornering it gives less.so no sensor for ecu to look at OR its there but broken/not working
 
edit-pop your steering wheel off,if you cant see a cut out on the boss for the `plug` on that sensor to go in(the black plug sticks thru the boss to turn the sensor.the yellow wire coming off is for the horn ..)

 
 
 

Lol, I changed my steering wheel with another one yesterday (no kidding!). I wish I would have known that before hehe. Oh well, I will remove it and check it out tomorrow.

I have had a look at this for alex and i think you're on the right track twomr2s im pretty sure all we were getting was the pump running for a minute then switching off but we tested the steering sensor according to bgb and it was flashing when turned more than 30° which is why we suspect the p/s ecu any help is appreciated.

Yeah, I couldn't see any sensor on the steering wheel, and the pump definitely turns itself off after 1 minute, then after another minute or so turns on again, etc...
Strange that the power steering doesn't always work for a minute after I turn on the car though?
http://www.mediafire.com/download/6r2cjihn6qr9kl8/PSpump.mp4