Toyota Electric Power Steering Conversion

Haven driven the All Trac without power steering for over a year, I came completely fed up with how much of a pain in the ass it is. I initially started down the road of putting a new rack (the existing was converted to “Manual” from the previous owner) with all the missing lines, etc. Well I started adding up the costs and even with junkyard parts I was looking at the upwards for over $300 to get everything back on. And since my engine is a 2nd Generation 3SGTE from an MR2, the accessories were all backwards. So the brackets would all have to change over to the Celica style. Well I stumbled across this thread one day:

It just made too much sense not to try it. So I had figured I would use a Prius Column and an early non-ABS Yaris ECU. Well it turns out you don’t have to have the Yaris computer and this is where the evidence came from:

So I found an 08 Scion XD in the junkyard a couple weeks ago and pulled the steering column and ECU out of it. I got the combo for just over $100.


Now I pulled my old column out


No joke, the column ways the same if not less than the factory one. The telescoping/memory column on these Celica’s are ridiculous.

Made some brackets to fit the Scion column to the factory mounts.


It turns out this column bolted right to my rack, U-joint and all, with zero modification to the rack itself EXCEPT for re-clocking the motor (and modifying the stock brackets). To re-clock the motor, simply put it in a vise or use a pipe wrench and turn the center section.


Here it is bolted up and the Scion turn signal and wiper switch wired to the stock harness.


IMG_0121.JPG 1 2

Now to power the unit all you need is a heavy gauge wire linked with a 40 Amp fuse to the battery, a fat ground wire and a small wire for the ignition to turn it on. For this unit the wiring was simple:


Big White -> Battery (40 A)

Big White w/Black -> Ground

Small Blue -> Ignition

Column covers trimmed and installed:

10 11

Now here is where the confusion comes in, how does it work on it’s own without talking to the ECU? Well I don’t know, it just does. My guess it’s a fail safe feature and its in that mode currently. After driving it, all I can say is that I am impressed. It is so easy to turn that heavy pig of a car now. However it’s a little too easy. So my future goal is too simulate the Toyota CAN system through inputs from my ECU. I will be converting the car to run on Megasquirt 3 eventually. There maybe sometype of interface Megasquirt can output a CAN signal to complete the RPM and SPEED requests that the EPS ECU is requesting. This should eliminate the “waking” of the column and the speed sensitivity.

Small video of delay in Limp mode:

Other current issues


Wiper Relay

The wiper relay seems to be different. After reviewing the scematics of both relays, it seems the Scion Relay has a Zener diode on the INT portion of the relay. I have no intermittent option on the switch, it acts as the slow wiper setting with no pause. Also the wiper does no clock properly, it goes past the zero setting. I would also like to note, DO NOT FOLLOW THE WIRING DIAGRAM ON THE SWITCH SIDE FOR THE CELICA. It’s ass backwards from the big black plug to the switches in some many ways. Gauges and colors are all wacky and not consistent. The body side is correct though.


Ignition Switch

The switches are similar in shape and operation between the two vehicles, however they do not interchange. The scion uses very light gauge and the Celica runs all the car power through the switch. A couple solutions would either re-pin the Scion plug with heavier pins or make an adapter to interface the Celica switch to the Scion ignition switch. The latter seems too time consuming and too many possibilities for failure.



Re-pin the Scion connector.


Summary so far

So far I like driving with it and am very pleased with the price of the conversion. I saved a lot of weight and utilizing the MR2 alternator position allowed me to keep a lower CG which is a big plus over having that Alternator way on top of the engine bay like the Celica comes stock with.


  • waid


    My investigation shows the same thing and I confirmed in Toyota Service Manual. The Steering ECU goes in to Fail-Safe mode after 10 seconds when it can not find CAN BUS.

    My 1964 Falcon has Electric Steering now but not derivable yet.

    Just wondering how many hours or mile have to put on this car with electric steering?

    There is my post with my pics and videos:


    • admin

      It’s been on the car for over a year with probably about 15k miles. Not a single issue so far and would trust it for the life of the car. But the goal is to run a canbus controller to talk to the ECU

  • waid

    What I found is that just about any Japanese or Korean brand car has Fail-Safe. Leave it GM and leave of Fail-Safe in Saturn Vue and Chevy Cobalt.


  • waid

    Is yours a race car ?

    • Jonathan

      Hey Waid been trying to get in touch with you can you check your PM’s on LS1tech thanks.

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  • Yash Trivedi

    Hey, I have a toyota corolla 2010 model.
    The vehicle’s engine has been removed, so naturally the EPS stopped working.

    Now if i go as per what you say, if i am able to manually give the ignition signal to the EPS, it should work in the fail safe mode.

    Now as per what i know, the vehicle speed is conveyed to the ABS first before the ECU as well. So i am guessing maybe the Vehicle speed signal reaches the EPS controller.

    But i am not sure what other CAn signals are necessary, and how to simulate them. I have tried observing the CAN traffic through a kVaser HSV2. But no luck. Without the DBC file of hthe system, it is a needle in a haystack kinda situation to figure out which ID sends the required signals.

    Any help you can provide. Which signals does the EPS demand via CAN? What are the IDs for the same? How to identify them?

    • admin

      You are correct, however I have none of those signals. I never got that deep into it, but I was going to use and Arduino with a CANBus shield to talk with the ECU to give it the speed.

  • john

    doing a conversion for mitsubishi jeep (j23a) think of it as a much improved cj3b with a diesel. ive got a vue column made up for it. the box came from epower steering.ive tried 2 different prius ecus 89650-47102 and for the life of me cant make it work and i suspect the torque sensor wiring at first i tried e power’s wiring colors which matches the prius pig tails on the plug. relay clicks wait as long as you want but no assist. there are 24 possible combinations and tried them all. no luck either ecu, maybe i ruined both ecu’s doing this.i know the sensor pairs as the ohm out 6.5 ohms.but i dont know which is left or right. any body have any idea what the connections are supposed to be,all the factory wiring diagrams are all well and good but one thing they omit is the vue box data. can anyone supply an answer? just ordered a 3rd ecu and i dont want to experiment any more

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