Aperture Controls

The 2015 Subaru WRX electric steering rack conversion


Electrical routing

Factory service manual pinouts

Here is the pinout to the control unit. Connector B goes straight to the battery and must handle at least 80 amps. I used 6 AWG cable going through a 100 amp circuit breaker mounted to my engine fuse box. Connector D and Connector C come from the rack. The motor is a 3 phase AC unit with an encoder. There's a third plug that comes off the rack that goes to the torque sensor, but it doesn't connect directly to the control unit, it runs through Connector A, which is where you'll spend most of your timebuilding a cable. The Connector A wires are all 20 AWG. I only had 18 AWG lying around to use, which made some of the pins hard to get into the housings.

Steering computer connectors

The top connector is Connector B, with Connector A to the right, and the plug that connects to the torque sensor on the rack on the lower left. I started going through the pain of trying to de-pin all this crap, but I gave up once I got to Connector A. I do have some notes, though. Connector A is made by Yazaki and is from the RH series. The housing is 7283-8856-30 and the terminals are 7116-4417-02. Good luck finding it. The torque sensor connector is made by Yazaki and is a 2.3II series. The pins are part number 7114- 4027. Here's where I found something interesting. General Motors has a terminal kit (made by Kent Moore) they sell to dealerships called the J-38125 Terminal Repair Kit. The pins for this connector are in Tray 11. I went down to my local dealership and after a bit of explaining, got two pins for free when I broke one of my originals.

Torque sensor pinout

This is how the torque sensor connector (the beige one) connects to Connector A (the annoying small black one.) When I finished my cables, they looked like this (the battery cables aren't cut to length yet.)

Steering computer mounting

My windshield washer hasn't worked since I bought the car, so that's where I mounted the control unit. I ran one cable over the crossmember, and the other underneath it, all secured with rubber coated metal brackets. The cables near the engine were then all covered with heat reflective tubing. The unit is mounted on 1/2" standoffs using one existing hole from the washer bottle and one that I had to drill.

Now that all the mechanicals are hooked up, and all the electrical is put in... we get to drive the car! No. I fired it up and had no power steering (I wasn't really expecting to.) I verified all my connections and signals. 12VDC to the unit. The CANbus was communicating so I know the computer works (more on that in a minute.) There was 5VDC to the torque sensor and it was giving 2.5VDC back like normal. The unit was pulling around 200mA when powered on, but that was about it. I can tell out that it's easier to drive without power on this rack than it is on the hydraulic (even with all the fluid out.)

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