E85 Electric Power Steering Control Unit Resoldering?

[matthijsfh]

Can you take some higher res photos of the board / repair? I'm an electrical engineer and could see about passing some insight.

First have to dig the unit out of the pile under the work bench. But I used my soldering microscope, and did not seen anything that looked like manual labor on the unit. All the thin wires are clearly spot-welded by a automatic process and the silicon stuff not was not touched at all.

Especially compared to the "open wound" of the capacitor replacement, it makes me suspect the capacitor is the actual repair. And my unit just failed. The way the unit died (starting the engine), and the life long warranty on the repair makes me believe the repair has to be rock solid simple.

BTW: none of the other boxes were opened.

Greetings Matthijs

 

[AlexG1080]

Hey everyone! I had the same issue as the original thread creator. I warmed up the control module with a hair dryer and it started working in about 30 seconds, which gave me the confidence that the EPS module was the issue. I finally got around to removing the whole steering column to send the control unit to ECU testing. I saw this video posted from ECU testing on YouTube https://youtu.be/lA1JIruh4DI?si=ApN-dFhkKI9Nz7QT about removing the motor/control module from the steering column and it looks different than the one I pulled from my 08 z4 3.0si. Mine looks like 2 hex bolts attaching the motor to the column. Do I have to worry about all the stuff in that video? Or can I just unscrew and pull the motor out? I’d post a pic but can’t figure out how.

 

[enuff_zed]

From experience it seems UK cars have torx head bolts but US ones have a female Torx head.
Other than that they are all the same.

 

[AlexG1080]

Hey everyone! Looking for some advice on my 08 z4 3.0si. I had intermittent power steering issues and sent the EPS module to ECU tuning where they said they found the issue and fixed it. After reinstallation, when I first turned the car on, there was no fault and thr power steering was working. When I was testing the steering full left and right, it threw a fault and stopped working again. I have a diagnostic scheduled tomorrow, but is it fair to assume the steering position sensor needs to be recalibrated? They want $180 just for a diagnostic fee, so wondering if I can buy a device and recalibrate myself . Any advice would be great, thanks!

 

[matthijsfh]

I have a diagnostic scheduled tomorrow, but is it fair to assume the steering position sensor needs to be recalibrated?

Hai,

Maybe a little late.... but the position sensor is NOT used by the power steering. The torque sensor is connected straight to the EPS motor and the prime input for the EPS to make torque and help you steering.

I think the position sensor (angle) is used by the stabilisation system.

Seems to me your EPS is dead and you need to source a 2nd hand one from eBay. That did the job for me.
Just make sure you get one with the correct LHD or RHD version of the software in it (LL = left, RL = right)

Grt Matthijs

 

[enuff_zed]

Maybe a little late.... but the position sensor is NOT used by the power steering. The torque sensor is connected straight to the EPS motor and the prime input for the EPS to make torque and help you steering.

I think the position sensor (angle) is used by the stabilisation system.

Or......maybe it is? :wink:

 

[matthijsfh]

Ohh did not know this.

Where did you get the screenshot from?

• Slightly weird that the EPS receives the day/night info and the km reading (unless km is used for error reporting).

• The sports button is hardwired to the EPS unit on an E85. Unless is it also hardwired to another ECU, the EPS is sending it value out over CAN.

Is this an official list?

 

[enuff_zed]

Ohh did not know this.

Where did you get the screenshot from?

• Slightly weird that the EPS receives the day/night info and the km reading (unless km is used for error reporting).

• The sports button is hardwired to the EPS unit on an E85. Unless is it also hardwired to another ECU, the EPS is sending it value out over CAN.

Is this an official list?

It's from NewTIS. So yes, very official.
I've copied the whole section for you (see below)
You will note that it is in fact the DME that reads the Sport button selection, then tells the EPS ECU. If the EPS is in agreement then it lights the button. So the Sports button is only 'hardwired to the EPS unit' to receive the light signal. The EPS ECU receives the Sports button info over the CAN, it does not send it out.
The vehicle speed is used to determine the amount of power assistance needed.

 

[matthijsfh]

Very cool! Thanks a lot.

I do not have access to this system, so this is very valuable.
Good to know the EPS controls the light.

 

[AlexG1080]

That may be possible, but it was intermittently working before I sent the module to ECUTesting and it was not having any torque sensor issues. I’m taking it to a shop today that has the ISTA programming that is capable of resetting the torque sensor. So far all been able to do is mess with the steering angle sensor.

 

[AlexG1080]

The EPS module was dead and rebuilt by ECU tuning. Upon installation, I’m assuming I destroyed the torque sensor by not being careful with how much the column was rotated. So ya it was repairable and now I’ve ruined it. On the plus side I’ve sourced all of the parts for a hydraulic conversion and I will never have to deal with EPS again. It wasn’t all a waste, I disconnected the EPS computer from the motor and it keeps my sport button functioning for the hydraulic conversion.