# Power Steering : Hacking a Hyundai EHPS



## Old.DSMer (May 18, 2012)

*Power Steering : Hacking a Hyundai Genesis EHPS*

I have been heavily debating the implementation of power steering in my conversion. Initially I anticipated using the factory pump off the auxiliary motor shaft. However, this ends up providing the OPPOSITE of what is required. Namely, more assist at higher RPM and no assist when still. Not the best for parallel parking. Most people want the most assist when still or moving slowly - and much less at high speed.

A popular option has been the MR2 pumps - specifically the 3rd Gen MR2 Spyder. Simple to wire, integral controller, and speed sensitive assist. Not to mention many validated implementations and lots of wiring diagrams. So why look elsewhere?

In Canada, used pumps often cost USD400 (and up!) off eBay (with shipping). MR2 Spyders are not very common and thus are rarely found at wreckers north of the 49th parallel. Not to mention the increased popularity amongst tuners and racers has driven the demand (and cost) of the pumps steadily skyward. So the motivation is cost and availability.

Enter: The Hyundai Genesis EHPS unit made by TRW. Also with integrated controls. I had hoped this was as easy as the MR2 and a sweet find for a fraction of the cost. Sadly, I'm disappointed. The unit does, in fact, have an integral controller - but its fully CAN controlled by the car ECU. I managed to dig up some information from the FSM and several systems are monitored by the ECU. The default failsafe is "Stop Control". So basically, without a properly functioning ECU, the pump won't run. It also has variable assist - controlled through CAN.


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## Old.DSMer (May 18, 2012)

*I'm Stubborn*

Being as stubborn as I am, I wasn't going to give up that easily. Internally a BLDC motor needs some kind of controller. Perhaps I could bypass the CAN system and tap directly into the motor FETs or the FET driver. So I opened up the case to see what I could find.

Some basic reverse Engineering revealed a few ICs, which I was able to download data sheets and get pinouts. This helped verify the +12V, GND, and CAN pins on the connectors.

ICs are:
1. TDK ZJY-2P02 : Common mode CAN filter
2. TLE 7469 : Dual rail 5V regulator
3. TLE 6250 : Highspeed CAN-transiever
4. Infineon SAK-XC164CS-16F40F : Microcontroller
5. MLX 15120DB : BLDC FET Driver
6. "EMS" : FET package

The MLX chip is made by Melexis. I contacted them and was advised the chip was proprietary, so I was unable to obtain the pinouts. I thought if I could manipulate the MLX through an Arduino, I might be able to build new control logic and utilize some of the internal circuitry and the neat FET package already inside this nice TRW unit.

*So far, this is a dead end and I'm open to suggestions on other things to try.*


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## Old.DSMer (May 18, 2012)

I have purchased a cheap BLDC motor controller from eBay hoping to tap directly into the motor connections and bypass all the internal electronics. IF (and thats a big IF) it works, I'll upgrade the FETs in the eBay controller - hopefully ending up with a high power drive side utilizing the China-"developed" control side. I would then simply remove all the proprietary control boards and mount the upgraded replacement system. Note there is a "SPEED" control using 0-5V input. This would be easy to regulate off the Vss signal and thus generate speed sensitive assist.

Currently waiting on the eBay controller.

This other thread started down this path, but has not been updated for a few months. Anyone know if its working???


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## Casper10 (Mar 8, 2014)

Old.DSMer said:


> I have purchased a cheap BLDC motor controller from eBay hoping to tap directly into the motor connections and bypass all the internal electronics. IF (and thats a big IF) it works, I'll upgrade the FETs in the eBay controller - hopefully ending up with a high power drive side utilizing the China-"developed" control side. I would then simply remove all the proprietary control boards and mount the upgraded replacement system. Note there is a "SPEED" control using 0-5V input. This would be easy to regulate off the Vss signal and thus generate speed sensitive assist.
> 
> Currently waiting on the eBay controller.
> 
> This other thread started down this path, but has not been updated for a few months. Anyone know if its working???


Hi Old.DSMer,hope you get it going,being stubborn is sometimes the only way to success. We did find however that the Astra/Vauxhall mk1 & mk4 units can be utilised and prices quoted by members range from $40 US, so if stubborness doesn't work talk to Sabahtom about the Astra units. All the best with it Casper10


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## Old.DSMer (May 18, 2012)

Casper10 said:


> Hi Old.DSMer,hope you get it going,being stubborn is sometimes the only way to success. We did find however that the Astra/Vauxhall mk1 & mk4 units can be utilised and prices quoted by members range from $40 US, so if stubborness doesn't work talk to Sabahtom about the Astra units. All the best with it Casper10


That's an awesome price. Even with shipping costs! Thanks for the info!


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## Casper10 (Mar 8, 2014)

Hi Old.DSMer. just got your reply from the Volvo thread,I wasn't questioning anything about what you were doing,just asking the cost I applaud what your trying to do it would make it much simpler if there was a conversion box of sorts available,just make it plug & play for people like me to install. While I can make up simple decoders for speedo input conversions for cruise controls etc what your talking about above is beyond me HeHe! 
Best Casper10


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## Old.DSMer (May 18, 2012)

*Marginal progress*

My eBay controller arrived and I quickly wired it up to test my alternative control theory. IT WORKS ! ! ! The variable speed controller generates an internal 5V signal to vary the speed - currently wired through the rheostat. I'm hoping to vary this based on an adjustable ramp fed from the Vss.

As you can see by the photos, its grossly undersized, but it did run the pump. By plugging the outlet hole visible in the middle of the pump, I was able to load it down to about 5 amps at 11V sag (pumping air) -- so only about 55W.

My next step is to find a damn adapter so I can hook up hoses and pump some oil. The factory line kit is over $600 and is only available as a "complete kit". DAMN. Why didn't they just use something more standard like an ORB. Argh....

So the stubbornness continues and after some measuring/searching, I found out this is using (what appears to be) a modified Staple-Lok end. So now to try find someone IN CANADA who sells these --- apparently they are more common in Europe. Obviously it doesn't use the typical staple retainer - but some kind of "flange" which is bolted to the housing. No problem. I can easily fab something - but I need to find the adapters or hose ends. The search continues....


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## sabahtom (Mar 1, 2011)

*vauxhall astra*

I've got a vauxhall astra MK4 EHPAS. About $80 including shipping from the UK. Not CAN.


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## Casper10 (Mar 8, 2014)

*Re: Marginal progress*



Old.DSMer said:


> My eBay controller arrived and I quickly wired it up to test my alternative control theory. IT WORKS ! ! ! The variable speed controller generates an internal 5V signal to vary the speed - currently wired through the rheostat. I'm hoping to vary this based on an adjustable ramp fed from the Vss.
> 
> As you can see by the photos, its grossly undersized, but it did run the pump. By plugging the outlet hole visible in the middle of the pump, I was able to load it down to about 5 amps at 11V sag (pumping air) -- so only about 55W.
> 
> ...


Hi Old.DsMer, told ya that stubborness is sometimes the only answer,glad you got it working,try and find some damaged pipes at wrecking yard and have a hose maker adapt the ends over to a new hose(over here we have pirteck & duffield etc),could be a cheap way out as they would not be able to sell them anyway,or just cut off the fittings and braize or s/solder on a common nipple. Regards Casper10


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## Old.DSMer (May 18, 2012)

sabahtom said:


> I've got a vauxhall astra MK4 EHPAS. About $80 including shipping from the UK. Not CAN.


That's a great price. So far none of the UK sellers have replied to me. I will keep trying. Thanks for the tip!


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## Old.DSMer (May 18, 2012)

Casper10 said:


> ...that stubborness is sometimes the only answer...


Heh..heh...very true!



Casper10 said:


> ...damaged pipes at wrecking yard and have a hose maker adapt the end...


Agreed. Unfortunately our North American rides always seem to use bumped pipe with metric threads. Nothing available with Staple-lok.

I've got some leads on hose ends and adapters. Hopefully they pan out.


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## rtz (Jul 3, 2013)

I just wanted to post this link for anyone in the future who needs an electric power steering option. This setup can be spliced into the steering shaft:

http://www.unisteer.com/electric-power-steering/search-by-product/electric-power-steering.html


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## Old.DSMer (May 18, 2012)

rtz said:


> http://www.unisteer.com/electric-power-steering/search-by-product/electric-power-steering.html


No doubt, very nice units. Unfortunately about a galaxy out of my price range


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## rtz (Jul 3, 2013)

The direct price is high; but it's several hundred less buying it from a dealer.


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## Old.DSMer (May 18, 2012)

rtz said:


> The direct price is high; but it's several hundred less buying it from a dealer.


Interesting. It is a nice fully functional unit that wouldn't require much fiddling to get working. Definite cost-benefit there for some...


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## Old.DSMer (May 18, 2012)

*Controller Update*

The Staple-Lok adapters arrived, but of course they are too small to properly seal in the TRW housing. So I've found some Polypak seals that "might" do the trick if I replace the standard O-ring. Waiting for those to come in.

And while waiting for the necessary hydraulic parts, I dug into the components of the eBay BLDC controller. It is, surprisingly, a decent unit!

The MOSFETS are Silikron SSF7509 - rated for 75V and 80A (13 mOhms at 30A) . The drive circuit uses IR2101 High/Low side IC's. And since its sensorless, it utilizes an LM339 comparator to measure and interpret rotor position. I don't know what the microcontroller is - but overall this is a nice little package with a simple (self-generating) 0-5V input controlling the speed.

As the pics below illustrate - the power traces will need to be reinforced to handle higher current. And the shunt resistor will be reduced to "fake" the micro into thinking there is less current actually flowing. So as long as the traces and wires get the proper treatment, I believe this little controller will handle my max power of the EHPS unit. The factory Hyundai spec is 80A. I'll most likely run less because I don't need the full assist of a luxury sedan, and I can adjust this by adjusting the shunt and letting the controller handle max current. The controller itself is also small enough to fit inside the factory TRW housing (if I remove the now useless OEM board). I might even integrate and use the factory power connections.

All this assuming, of course, that the hydraulic output is sufficient and the custom seal works.


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## mu2b (May 5, 2015)

Dear Old.DSMer: I just found your post. I just got through installing the very same TRW pump in my 79 Dodge Ram 1500. I had stopped at the Hyundai dealership to get some info as to wire the pump. I have had no success so reading your post was very helpful. Thank you. Could you please help me replicate your system. I don't think I need a rheostat because I will use the pump only during parking, so that it would need to be at 100% or off. I found this on eBay (item 201343464848) however it's limited to 15A. I was thinking the need could go as high as 80A. Any help is appreciated. Thanks. Luke


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## Old.DSMer (May 18, 2012)

Hey mu2b, I'm long overdue on an update to this thread.

Long story short, it worked great for about 30s. And even though I beefed up the board traces, they still overheated and failed. During the test, all the hydraulics were good and didn't leak. So the custom adapter and seal held up.

I've since upgraded to a high power RC controller. I need to write a small program on a PIC to run it. So that's next on my to-do list. I'm currently trying to repair my Soliton controller. Which didn't like the motor shorting out which I outlined in my other thread. So the power steering project is kind of on hold for now. I'll update again when I get back to it.

Good luck with yours, and please update if you find another alternative that will work.


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## squeegee (May 13, 2011)

I know it's an old tread but I am potentially looking at needing to do this...If my EHPS does not work as I would like (yet to be fully purchased and assembled)

So why stay away from CAN bus?... , for my hacking I though of using a CAN steering angle sensor kinda what done here:
http://imgur.com/gallery/TM6lp
Angles should be angles and turn rate is turn rate right?

Maybe couple that with an arduino CAN OBDII module:
http://arduinodev.com/connect-arduino-to-a-car-through-obd-ii-port/
you could send a low speed "indication" (5mph?) when in 1st or Reverse (assuming your motor is mated to a transmission) and a high speed signal (50mph?) otherwise.

well my 2c anyway


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## squeegee (May 13, 2011)

actually, just use this for speed:
http://www.microchip.com/forums/m427967.aspx

edit: OOPS that's for an ABS sensor... but it should work.


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## squeegee (May 13, 2011)

Wow, even with an arduino doing the work, get the GM steering CAN info to a Volvo one could be a tough puzzle, especially since Volvo seems to have put in a lot of their own sauce into this.

Can't tell if the Volvo steering interface is directly CAN or converted by the CPU. 

As for the VSS signal, lots of devices convert it from CAN, but not back...the ABS speed sensors have their own ID so could be used and converted by Arduino

And here I though CAN was CAN, now I am hopping I don't have to go there.


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## Old.DSMer (May 18, 2012)

*Re: Power Steering : Hacking a Hyundai Genesis EHPS*

LOL....yep. All proprietary. I do not have a working system to sniff packets. If that was available, you might be able to spoof the messages and send the minimum possible to get it running.

Regarding my Hyundai unit, I have successfully run it with the RC controller driven with simple code on a PICAxe. I had to add an external relief valve to prevent the RC controller from stalling when the steering hit full lock. So either this unit has no internal relief, or my RC controller hits its power limit first. With the external relief at 600psi, it works flawless. Right now, all my hydraulics are installed and working. But I have yet to finalize my code and install the electrical.

Sent from my HTC One using Tapatalk


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