Hi All,
 
Recently bought a 1990 JDM SW20. Power steering does not work and the light is on the combi meter. 
 
- Checked the relay problem, relay has already been replaced with a nice big solid state one, relay switches when you turn on ignition. 
- No codes in the system and all wiring looks good (after replacing a few destroyed wires)
- Motor brushes OK
- Pump does not turn on, but does work when you put 12 V + proper ground on the pump
- Seem to have power on the pump normally, but service manual implies it varies the earth resistance via the pump driver ecu.
 
- Looks like the ECU or the pump driver never seem to fail, so I am leaving that to last
- Steering angle sensor doesn't seem to be outputting any change of voltage, but power steering should still probably turn on while driving from the speed sensor.
 
Anyone had similar problems or have any suggestions? My next thought is to try and pick up both ECU's cheap and just swap them over to try..

I haven't done any electrical fault diagnosis before with the MR2 steering system so can only go off what's in the BGB.
 
Did you check the steering sensor IAW the BGB? it doesn't mention measuring voltage only resistance (I realise one will effect the other).
 
Odd no codes are being stored, if the light stays on that means there is an error and as such should be a code? meh.
 
It definitely sounds like a control issue as you have proved the motor works, all you can really do is just test all components/loom as per the BGB, boring continuity tests and the like.  Swapping the ecu for another would be quick an easy but then spend 30 mins doing the necessary tests and you'll find out either way if it's good or not.
 

What state are your in? I have a spare powersteering ECU.
i went through similar pains. Check your speed sensor wire is telling the ECU it's doing less than 40 for it to trigger it to come on. Check the steering column positioning / turning signal wire.
Mine end up up being a soft application of sandpaper on the bushes, speed sensor signal, and working again. So I have a spare power steering ECU that I paid way too much for but happy to part with.

Hi Guys,
 
Thanks for the replies! 
 
Yes - I have no idea why there are no codes. On diagnostic it just flashes consistently. Just found many more checks in the BGB, so lots of continuity checks can be done. Steering sensor could be an issue given that it looks like it has had a replacement wheel at some point in its life. Could have been fiddled with...
 
Thanks for the offer Tony - I'll try and hold off on buying ECU's until I have exhausted all options.