z4 EPS question!

[Mycheapz4]

First post for my new to me z4. The previous owner did struts and shocks and sold it to me with a host of problems. The main one that he noticed after the strut change was that the EPS light came on and that for the first 30-45 seconds of driving, the power steering doesn't work. after the 45 seconds are up, the power steering works fine for the rest of the time you are driving the car. I haven't got a scanner yet, but wondered if it could be related to the steering angle sensor needing recalibration? because it works flawlessly after the first dead time, I don't think it's the actual EPS motor, but wonder if anyone has come across this issue? Thanks in advance!

[BR54X]

Im not 100% sure about the problem in your case but when I got my car sometimes the EPS didn't work and it was caused by a bad battery. The best thing would be to check for any codes as they can point to the issue. One thing you can start with in the meantime is to have your battery checked to make sure it is good to rule it out of the equation.

[enuff_zed]

Mycheapz4, where are you?
Need a code check first and take it from there. Possibly the EPS ECU on its way out but ideally you need the code reader connected to check when you first start up. When it is failed does the sport button work?

[Barty]

Welcome! “A host of problems” combined to your EPS woes sounds like a bad battery to me. Have you tested it? Our cars are woefully sensitive to electrical instabilities

[Philco]

EPS issues on Z4 E85 : my personal experience, hope this could help some E85 owners.
Hi,
I had an EPS issue 2 years ago. No power steering at all, error light of EPS ON on dashboard (permanently). After diagnose, there was no communication with eps ecu : I made it fixed by a specialized ECU-repair service.
It worked perfect 3 month ago.
After this I had intermittent issues (no power steering , intermittent error light shining). Diagnose was : "low voltage". So I tested voltage and ground at the electric motor of the EPS,tested alternator voltage, battery and it was ok. I decided to go further to have a good electric circuitry and I cleaned all the ground points (on the body of the car).
Problem disappeared for more than 36 month.
After this, I had intermittent issues again (No power steering and error light of EPS error shining), and the steering was "floating" on all kind of roads... But no EPS failure on electronic diagnose. I decided to verify the front suspension triangle because of the strange behaviour of the car. The right side silent bloc was in a very bad condition... I replaced both silent blocs : EPS issue disappeared now, the steering behaviour of the car is now fine as well.
I think that the strange behaviour of the right suspension gave strange information to DSC (dynamic stability control) via the DSC captor situated on the right suspension triangle and gave probably that error. It is important to know that DSC, ABS and EPS are influencing each other.
So, before changing an entire steering column by a new expensive one, be sure everything is in perfect mechanical and electrical condition everywhere else. Make a good electronic diagnose and read the codes.
If you need some WDS or other diagrams or photographs concerning those issues, I can provide them.
Philippe