ElectricSubaru


Last update: Dec 26 2016

Power Steering

The Pump

The electric power steering pump is a from a Toyota MR2, 3rd generation. The part number is 4431017060. I got information for using this pump at honda-tech.com, diyelectriccar.com, and simonfamily.us/FocusEV/.

Toyota MR2 steering pump 4431017060 Toyota MR2 steering pump pinout Toyota MR2 steering pump circuit diagram

The electric connectors are expensive at about $55, so try to get them with the pump.

PartDescriptionQty
90980-12068Large connector housing1
90980-10897Middle connector housing1
90980-10942Small connector housing1
82998-12500Large connector pigtail2
82998-12440Middle and small connector pigtail3

Pump Mounting

The pump shares the bridge with the motor controller. One of the pump's three mounting holes is at a bit of an angle. A small clip converts from Subaru flatland to Toyota slantyville. It is 1/8in aluminum bar bent into a U shape, then subjected to power sanding.

Mount angle Mount angle Mount

Power Steering Fluid

The Toyota MR2 steering pump specifies right on the cap to use Toyota Power Steering Fluid EH, part number 08886-01206. So that's what I used.

Fluid

Draining the fluid is simple. Remove the jack up plate (aka support arm), unhook the exposed hose at the LH end, turn the steering wheel slowly. To replace the fluid, fill the tank half way, turn the steering wheel, run the pump, wait a half hour and repeat until no bubbles appear in the tank.

Jack-up Plate Fluid Draining

Replacing the jack-up plate presented a bit of a puzzle. The service manual specifies a preposterous torque value of 52 ft·lb (T9) for the middle four M8 bolts. By contrast, the specification for the outer M10 bolts is 22 ft·lb (T3). The 2002 service manual specifies 14.5 ft·lb (T1), for the corresponding middle four bolts, which seems reasonable.

Jack-up Plate Torque 2002 Jack-up Plate Torque 2006

Custom Hoses

The new Toyota pump is in a different location and has a different thread size output than the Subaru pump. PIRTEK fabricated new lines. They cut the fittings from the bottom end of the existing lines and brazed them to some fittings that attach to new soft lines. The high pressure line has a new banjo fitting sized M16x1.5 for the Toyota pump. The Subaru pump is M14x1.5.

Lines Lines Lines Lines Lines

Rotating the plastic tank on the pump 90° counterclockwise routed the hoses a little better.

Pump tank Pump tank

Electrical

Power for the pump comes directly from the 12V battery through a 50A self resetting circuit breaker then through a 50A relay that is energized when the ignition is switched on. These components are mounted between the battery and pump, to keep the wires short.

Breaker and Relay Breaker and Relay

I measured the pump current draw using a 100A ammeter.

StatusCurrent
Maximum force47A
Idle less than 1 minute6.2A
Idle 1-2 minutes 3.9A
Idle more than 2 minutes2.3A

Ammeter

Vehicle Speed Sensor

The steering pump normally receives the vehicle speed sensor (VSS) signal on connector P7 pin 2. I left the VSS pin unconnected. I think the pump uses the VSS primarily for deciding when to put the pump into a lower power mode for saving energy. The steering feels normal without the VSS connection.