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:

 http://www.toymods.org.au/forums/engine-driveline-conversions/79652-electric-power-steering.html

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.

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Now I pulled my old column out

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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.

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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.

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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:

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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.

 

Solution:

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.

6 Comments

  • waid
    October 14, 2016 - 10:28 am | Permalink

    Hello

    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:

    http://forums.vintage-mustang.com/mod-custom-forum/974337-another-unisteer-problem-2.html#post8485722

    Thanks

    • admin
      October 14, 2016 - 11:47 am | Permalink

      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
    October 14, 2016 - 3:21 pm | Permalink

    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.

    Thanks

  • waid
    October 14, 2016 - 5:42 pm | Permalink

    Is yours a race car ?

    • Jonathan
      March 2, 2017 - 11:27 am | Permalink

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

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