RED Triangle light on (PS) off

The power steering motor is just an "armature permanent magnet field" type motor and can easily be checked by disconnecting it at it's connector then supplying it with 12volts. The steering will move one way and then the other when the connections are reversed. No movement probably means worn brushes as NH70 says or burnt out armature caused by holding the steering on a full lock.

 

Yes, that sounds like a reasonable move especially since that is the action recommended by your dealer.

 

This will require a zero point calibration by the dealer. Hope fully the motor will be OK and not be the cause of the failed ECU.

 

Yes, you can buy the ECU and plug it in, then have someone else do the calibration.

You can call around but I would expect that your local alignment shops will not have access to Toyota Techstream.

 

Intermittent problems are the bane of electronics troubleshooters. You can be sure it will act up again at some point. Things don't fix themselves, despite wishful thinking. You may have a loose connector somewhere, or else the motor brushes are maybe stuck and not connecting properly. It will take some poking around to see, but you could just check all the plugs first and make sure they are seated properly.

 

I would go with worn or stuck motor brushes, but now you have a spare ECU if it happens again you could change that out first. If that does not cure the problem try powering the motor directly.

 

Checking the motor brushes will mean partly dismantling the PS motor.

The brushes are two small carbon blocks that are spring loaded on to the armature ( the rotating part of the motor ). These often stick in the brass tubes they are supposed to slide in, or they can just be worn out and need replacing.

Domestic appliance repairers often stock brushes for vacuum cleaners/washing machines just a matter of getting correct size or slightly larger and filing down. If you are not happy doing this sort of work or know someone that is your only choice is a salvage unit or new replacement.

 

The ECU is easy to replace price is difficult for me to tell since I am in the UK But, I have seen others on PC buy them for $75 so look around.

The motor brushes are not difficult to repair/replace if you have done this sort of thing before or know someone with some knowledge of DC motors.

 

My P/S went out last night. I took it to the dealer today and when gave them the keys, it wasn't working. About 2 hours later the service advisor came out and asked me how often this happens. He said they couldn't find anything wrong and they would have to wait until it wasn't working. In short, somewhere between the reception area and the service bay, it fixed itself. My question is, did your issue come back? If so, did you ever find out what the solution is and if so, what is it?

Take care

 

Any more news on replacing the ECU?
I have a similar problem on a 2006 Prius, but no DTC. My steering is just heavy at slow speed.
I have diagnosed the EPS ECU and steering angle sensor and I have noticed the following:
- voltages on the EPS motor terminals are too high, when turning the wheel the voltage on one of the terminals should be above 10V and on the other below 1V. In my case both are above 5V. I suspect the electric motor/brushes, higher internal resistance thus higher voltage.
- the steering angle sensor (SAS) is constantly sending 1150 deg readings. After resetting the ABS ECU, the readings change as I turn the wheel, but goes back to 1150 as soon as I restart the car.
From the above and based on Toyota's repair manual, I could have the following faulty parts: EPS ECU, SAS, EPS motor and even ABS ECU. Since I have no DTC, is very difficult to track down the faulty part.
This could get nasty, as I am starting to suspect that the dealer has replaced some of my EPS parts with faulty ones from another car in February this year. Why am I suspecting that? Well...Prii are not very common in Eastern Europe and it happened that a Gen2 pulled into the dealer's parking lot at the same time I did back in February when I went for the steering column recall. They have checked and I didn't need a new intermediate shaft but it took aprox. 2 hours to inspect. A month or so after, when changing my winter tires with the summer ones, I have immediately felt a much stiffer steering.
Any advice will be much appreciated.

 

The Power Steering motor is a bidirectional DC unit that is controlled by a "H bridge" output circuit. So either terminal can be at 10V or at 0V depending on direction. If no motor power is required, then both wires will be at the same voltage, or 0V across the motor, and it will not run. If the motor was showing high resistance due to brush wear, those terminals will still go up and down just fine. I think there is no control signal being output from the ECU, and your voltage measurement agrees that the ECU is at fault, not the motor. We have seen other examples of PS ECU failure without DTC being set here on PC, if I remember correctly.

 

Thank you for the clarification, I agree. When no turn command goes to the motor, both terminals should show 5.8V, as per Toyota's manual. In my case the voltage is 6.9V on both terminals with no load on the PS.
None of the two terminals goes below 1V when they should, i.e. when turning the wheel in one direction or the other.
If EPS ECU has been replaced without giving any DTC, then this should be the easiest route I should take, replacing the ECU.
Is it just a coincidence that my SAS is acting weird too? I was thinking that, due to the SAS signal into the EPS ECU via the ABS ECU, the PS computer gets conflictual data and thus gives wrong command to the motor.
Might be a good idea to change the SAS too, although that comes together with the spiral cable.

 

There are a number of DTC's that should be set for PS motor malfunction, and also for torque sensor malfunction. I don't recall anyone seeing those parts go bad, but several have reported PS ECU going bad. With no DTC, I would more suspect the ECU has gone deaf/mute, rather than the motor or SAS not working.

But yes, it is hard to be certain, sorry to say.

 

Thank you for your support, I will continue to investigate and report back when the culprit is found .