Steering issue under braking !

[ML]

Originally Posted by RedReplicant

The answer is ... $4700

[RedReplicant]

After digging around a bit, it seems like these EPS systems are fairly standardized.

A lot of them used in the BRZ, Lexuses, Priuses, Versa, etc are a variation of the JTEKT C-EPS system. The columns are pretty similar other than the angle of the motor, shaft length, etc for the application.

The main thing I see is that the BRZ/Lexus/newer Prius have a three wire motor, and the older Prius/Versa/etc have a two wire motor. The other main thing that appears to have changed is the coupling from the motor to the column.




imo, the DCE kit is probably two wire motor that you can get for a Versa, Prius, etc and two CNC adapters. One adapter is basically just to space the motor back off the column and rotate it some number of degrees so everything can be bolted and the other is to internally adapt the two coupling types.

DCE Motor:



Random 2 wire, in this case a Versa



I'm sure their controller is really nice, but this is another spot where an off the shelf controller can be used along with an interface between the controller and stock CAN.

Long story short, I've got two ideas

[Opie]

So after never experiencing this issue before, after 6 years of tracking it happened to me for the first time at Barber Motorsports Park earlier this month. Complete loss of power steering assistance at T13 and having to Hulk steer it over the hill at T14, then it would come back and be fine until T13 again.

After getting home I reached out to my Subaru engineer friends regarding this problem. Here is what I found out....
Since 2012 there have been no issues of intermittent Electronic Power Steering (EPS) loss reported to SoA. That doesn't mean that people didn't report it to their local dealerships, but no dealer relayed that info to SoA or consulted their Tech line for assistance.

Worldwide there have been many reports of issues. So many in Australia and Asia that recalls were initiated. In the investigation into the cause, Subaru/Toyota found that the harness leading to the EPS computer vibrated during normal driving, and after time the vibrations caused wear to the metal pins and contacts in the harness connector. This wear creates a metallic, conductive, dust inside the harness connector that can create intermittent shorts between the pins in the connector resulting in the intermittent power steering loss.

What is the recall fix in Australia/Asia?
1. Remove the EPS module and bracket from vehicle.
2. Clean the harness plug, and harness connectors.
a. Using compressed air blow out harness plug and connector
b. Clean with electronic contact cleaner, let dry
c. Blow out with compressed air again
d. Sparingly apply di-electric grease to harness plug and harness connector
3. Remove bracket from EPS module
4. Install updated bracket to module
5. Reinstall EPS module with updated bracket.
6. Using Techstream or SSM, Perform Steering Angle Sensor Recalibration procedure

I did this install/repair to mine today. Will report after my next day on track if I have any more EPS loss issues.

Updated bracket is available in the United States, it is P/N: 34715CA011 and fits 2013-2020 Models of the BRZ, FRS & 86. 2016 and newer models should already have this bracket. EPS module does not change. New bracket is around $18

Why wasn't it a recall here? Most likely due to the no reports of issues to SoA and very few issues reported to NHTSA.

Also, there are 8 different variations of the EPS Module, this bracket fits them all:
34710CA010 - Build dates from Nov 11, 2011 to Apr 30, 2015 – All Models
34710CA030 - Build dates from Feb 01, 2015 to Nov 01, 2015 – All Models
34710CA071 - Build dates from Nov 02, 2015 to Jun 30, 2016 – All Models
34710CA050 - Build dates from Apr 01, 2016 to Nov 20, 2017 – All Models
34710CA110 - Build dates from Aug 01, 2017 to Aug 31, 2018 – All but Ts Models
34710CA130 - Build dates from Aug 01, 2017 to Aug 31, 2018 – Ts Models
34710CA150 - Build dates from May 01, 2019 to Dec 31, 2020 – All but Ts Models
34710CA170 - Build dates from May 01, 2019 to Dec 31, 2020 – Ts Models
Don’t know if they are interchangeable…..

This is only to address intermittent EPS loss issues, not to add custom programability like some of the other posts are referring too.

[RedReplicant]

I will try this, thank you for posting it. I am skeptical that it'll fix the issue here, but it is worth trying.

[Ohio Enthusiast]

IIRC people have reported the same steering issue with 2017+ and 2nd gen as well.

[Opie]

Originally Posted by Ohio Enthusiast

IIRC people have reported the same steering issue with 2017+ and 2nd gen as well.

Since there are no changes to the harness, or the EPS module, I would surmise that the cause may still be valid, and the bracket is just a measure to reduce the issue’s frequency. Routinely cleaning the dust may be more effective than replacing anything…

[RedReplicant]

There may be more than one "issue" at play here. I'll be cleaning my connector out and testing it in a few weeks too.

After playing with the Prius and BRZ column, the motor drive ratios are different - ~15.25 motor turns to one shaft turn on the Prius vs ~18.5 motor turns to one shaft turn on the BRZ, which more or less precludes adapting the motor and using the Prius controller (changes how the controller would control the motor for assist, return to center, etc). I will try bolting the Prius column in the car after my last event until summer break, it has some differences but it might fit.