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Power Steering using Toyota MR2 EHPS pump

223264 Views 72 Replies 39 Participants Last post by  remy_martian
Many EV conversions have to deal with Power Steering decision. If you decided to keep PS and looking how to drive PS pump, consider this all-in-one solution brought to you by Toyota engineers. Toyota MR2 has EHPS ( Electric Hydraulic Power Steering ) in which pump is driven by its own electric motor instead of pulley hanging off the main engine like most ICE cars do. First generation of MR2 had separate fluid tank, motor/pump assembly and controller, some EVers took motor/pump and wired it directly to 12V or via various switching circuits designed to keep the pump off while driving straight or at high speed to save power.

However, 3rd generation of MR2 also called Spyder has a single pump assembly combining motor, pump, fluid tank and controller, making it very attractive option for EV community.

To the best of my knowledge you are looking for 2000-2005 ( maybe some other years, I'm not sure ) EHPS pump from Toyota MR2 Spyder, call your local junk yards or check this one online . The pump looks like this:

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To wire it use schematics below. If you don't have proper harnesses you can either solder directly or create your own connectors for each pin. I personally created connectors and then filled harnesses with caulk to keep wires in place. It can be removed later if needed.

Passive circuit component Circuit component Diagram Plan Technical drawing
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Although 50 Amp relay is stated, I couldn't find one so I used typical 40 Amp automotive relay, my testing shows that it doesn't actually reach 50 Amp current anyway.

You can wire VSS signal from your car to make the pump turn itself off at higher speeds, but I couldn't manage that because my Miata has unusual VSS signal. Even without VSS, the pump runs idle at 4 Amps until you actually turn the steering wheel, so the power wasted is very minimal.

You'd have to find a way to connect PS Pressure line from the pump to your car's rack and return line from the rack back to the pump. Return line is easy, just use 3/8 hose and clamps. As for pressure line, if you are lucky you can fit one from other Toyota models, if not, you can make custom one from separately purchased fittings and the pressure hose, I have seen those on Ebay and online shops like this one

Hope this helps, feel free to update this Wiki with more details, my main goal was to publish schematics and wiring, I am not very good with hydraulics, maybe someone can add details on making custom pressure hose.

Here are the Toyota part#'s for the electrical Connectors: These part#'s get the Plastic part only, The metal pin wiring parts are sold separately. Maybe someone can add the part#'s for those.
Part#'s Large connector 90980-12068
Middle connector 90980-10897
Small end connector 90980-10942

There are two part numbers for the wiring. They come with the plugs, rubber seals, & about 6 inches of wire. At $6.55/ea they aren't cheap for what you get, but they are made to fit.

Three pigtails for the small & middle connectors P/N: 82998-12440
Two pigtails for the large connector P/N: 82998-12500


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Could not confirm the size of the fitting. I'm almost certain the size I quoted. Here are a couple of pictures of my fitting.
I bought it from a hydraulic supply company in medford Oregon.

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Hey, I have a 3rd gen MR2 Spyder pump wired up in my subaru. Everything seems to work right except there is a lag in the pump coming off idle to on a pressure drop from a quick steering input. As well it doesn't seem to respond to the VSS input.

I have been able to flash out ALL the codes, almost every one there is. Only problem is I cant clear them by toggling the Ts wire from ground.

If anyone still watches this thread and has any insight please let me know. Thanks
I have read many various website threads talking about MR2 EHPS in non-electric vehicles and they all seem to stress 75-80 amp relays and circuit breakers and 100 amp alternators. My question is if the 2001-2005 MR2 alternator was only 80 amps, why all the large amp relays/circuit breakers for a non-electric,(in my case a 1995 240SX with RB25DET, series II) when I have no large amp devices installed like large amp amplifiers and/or off-road lighting, etc.?

Also, I plan to use the RBs VSS signal to feed the 3rdgen MR2 EHPS. The RBs ECCS has the VSS on the tranny feeding the speedometer from ECCS terminal 53. Any advice on the correct wiring to EHPS middle plug would be very much appreciated.

Same for the RBs power steering oil pressure switch signal which is a 2 pin plug with pin one to ground and pin two to terminal 19 on the ECCS
Hey all,

I've been roaming around these parts for awhile as you have great information regarding steering and brake options. This is my second time registering (had issues logging in) And my first post. I am currently running an mr2 Spyder steering pump and almost went with a hydra boost setup however never really could find a good answer to how well it worked with this pump..So I went vacuum assist route.

My question if someone could help is that my MR2 spyder pump when wired according to the diagram wont run. My relay went bad and when I replaced it would no longer run and simply pulse blew. I ended up running an ignition switched power to the pump switch(its relayed) and a 50 amp self resetting buss to the motor directly from the battery to power it, and now it works. VSS was never hooked up. So my question is can someone post a photo of their relay wiring? I don't know if I missed something along the way but Id prefer to have the pump on a relay. I cant tell you HOW frustrated I was!! Many Thanks

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Does anyone know what type of speed signal Toyota MR2 EHPS´s ECU understands? Regular square type signal coming from Hall sensors?

Just hooked up the 2000-2005 MR2 pump and it appears to be running backwards? Does anyone know how to fix that? I've followed the diagram in the original post exactly.
Planning to find one of these for my 99 neon. I have a 2000 style neon pump in as it moves the resevoir to the top of pump to clean up engine bay, but the pump resevoir cap pukes fluid back out, as did my stock one on the back of the engine. Sick of the drips. but also of the squeals as I have an underdrive pulley. The 3rd gen is all self contained and not needing the actual ECU from the car correct? Is all that is needed is the whole unit and the plugs? And does anyone know offhand if the VSS from a 99 neon will work with it?
Thanks all.
Would someone double check my homework?

I am using OPs guide:

and this diagram

and came up with this:
Untitled by novablue454, on Flickr

Relay 30 to Batt 12v
Relay 86 to switched 12v
Relay 87 to Pump Large Connector pin 1
Relay 85 to Pump Center Connector pin 5
Pump Large Connector pin 2 to Chassis Ground
Pump Small 4 wire connector pin 1 to same switched 12v as Relay 86

What has me confused, is that in every diagram I can find replay pin 85 goes to a chassis ground, but the diagram in the OP has it going to pin 5 of the center plug. Is pin 5 just a ground source? If so, what is the purpose of using it rather than a chassis ground point?

Also, what is the relay even doing in this system? Seems that just running a constant 12v source and ground to the 2 pin connector, and a switched 12v to the 4 wire connector pin 1 would achieve the same thing with a lot less wiring and headache? But I am also an electrical idiot, so I'd like to understand why I am doing what I am doing.

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Hello, I read your post. Very interesting and informative. I want to put an Electric power steering pump in an older Mercedes. The car has a re-circulating ball type steering box. Not a rack. Also, there is no source for a speed pulse signal. Can it be done> Suggestions please? Regards.
Did anyone ever get to the bottom of the pump running backwards? I have hooked up my pump exactly as the schematics and it runs, but has only swallowed a small amount of oil and appears to be running at full speed but not providing any assistance. The oil level appears to rise when the pump is running and therefore I believe it is running backwards.
Thanks in advance
Just for anyone reading this and struggling like I was.

Take the motor cap off (where the stator magnets are glued), spin it 30° to the next fixings holes and try again. The arrangement of the magnets inside means if the motor cap is removed and fitted wrong the motor will spin backwards.

You will need to test the other two positions to figure out which has most torque.
I am building a small front end loader for my lawn tractor. I am going to use this pump as the source
of hydraulic pressure to move the Hydraulic Cylinders that move the bucket tilt and and lift arm. I will be powering it from a hefty lithium battery but would like not to drain the battery if I'm not using the pump.

I just want it to run any time while I am moving the bucket and turnoff when the bucket is stationary. This will prolong the battery life. so my question is the pin labeled (speed pulse) an input ? Is that what is used to turn the pump on and off?
You should contribute to future readers by posting the pinout that you know.
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