A slightly puzzling situation - self repairing Z4

[Mygreyzedder]

I wonder if any geniuses can help with this puzzle…

Couple of weeks ago my 2013 sdrive20i started showing a load of warnings:
DBS fail (braking and stabilisation)
Parking brake fail
ABS fail
Flat tyre monitor fault.

Also shortly after, the engine light came on on the dash along with “fault in drive” warning - possible to continue journey.

I had a local garage plug in the fault reader and they diagnosed left rear wheel speed sensor failure. Makes sense with all the braking related warnings, although not sure how it relates to the engine light / fault in drive. Booked it in for the sensor replacement.

A couple of days later, pulling off the drive very slowly, barely any accelerator, the car made an audible ‘clunk’ and gave a perceptible jolt. It sounded and felt somewhere below / behind the seats. Had a good look and I hadn’t run anything over, and I have been monitoring and no sign of any fluid leaks under the car.

Here’s the mystery… Since then all the failures and warnings have cleared completely and not returned, including the engine light and drive fault. Car seems to drive perfectly normally.

Has it somehow jolted itself better? Or maybe the whole fault warning system has failed? (Although FTM and engine oil quantity sensor etc all working fine). Any thoughts on this would be really helpful. I will take back to the garage for the wheel speed sensor replacement, but when I explained the situation over the phone the technician was as baffled as me.

Thanks!

[pvr]

Is the sensor on the E89 on the left rear wheel? On the E85 it is on the right rear one.

[Trav]

Try doing a tyre pressure monitoring reset as if you were doing it after a puncture or blowing up the tyres. I don't think it would work if one of the wheel sensors was still failed. I take it this is a daily runner so not like the handbrake stuck for the clunking and the initial failures were due to low battery.

[Mygreyzedder]

PVR: I’m not sure to be honest, I may have misremembered which side the chap said. Whichever side, they have ordered the appropriate part.

[Mygreyzedder]

TRAV: Thanks, I’ll give that a go. Although of course now there are no warnings to clear as it thinks it’s perfectly ok. The FTM system is showing as working and green for all wheels.

Yes, daily runner, 95000 miles

[Zedebee]

It is possible you had a stone stuck somewhere that was interfering with the wheel speed sensor, which you have now dislodged hence the slight clunk and jolt.

Obviously can’t prove it, but your problem is fixed so all good.

[Mygreyzedder]

It is possible you had a stone stuck somewhere that was interfering with the wheel speed sensor, which you have now dislodged hence the slight clunk and jolt.

Obviously can’t prove it, but your problem is fixed so all good.

Thanks Zebedee, that was the only thing the mechanic I spoke to could think of too. If it’s the case then happy days. My main concern was that the brake related / engine drive faults are still there but just not showing. In your experience is the self-monitoring of faults pretty reliable?

[enuff_zed]

Is the sensor on the E89 on the left rear wheel? On the E85 it is on the right rear one.

I think they all have sensors on every wheel, otherwise the DSC wouldn't know which wheel was slipping etc.
The one on the left rear of the E85 is the one that signals the speedo too, maybe that's what you were thinking?

Maybe the parking brake was sticking a bit on one side and has now freed itself?

[Mygreyzedder]

Is the sensor on the E89 on the left rear wheel? On the E85 it is on the right rear one.

I think they all have sensors on every wheel, otherwise the DSC wouldn't know which wheel was slipping etc.
The one on the left rear of the E85 is the one that signals the speedo too, maybe that's what you were thinking?

Maybe the parking brake was sticking a bit on one side and has now freed itself?

Thanks for your reply. I think it’s unlikely it was the parking brake sticking, I rarely use the parking brake and hadn’t used it prior to the fault initially appearing.

Is it normal for a wheel / braking fault to also being on an engine light and the “fault in drive” warning?

[enuff_zed]

Is it normal for a wheel / braking fault to also being on an engine light and the “fault in drive” warning?

I have seen it happen on an E85, as the DSC system cannot accurately determine wheel speeds etc it affects the power output from the engine, which in turn can sometimes cause an engine fault to be registered.

[B21]

Is it normal for a wheel / braking fault to also being on an engine light and the “fault in drive” warning?

I have seen it happen on an E85, as the DSC system cannot accurately determine wheel speeds etc it affects the power output from the engine, which in turn can sometimes cause an engine fault to be registered.

[Mike6]

You can get that noise if a brake caliper has been sticking a bit and suddenly frees itself. That account for the codes.

[Mygreyzedder]

Is it normal for a wheel / braking fault to also being on an engine light and the “fault in drive” warning?

I have seen it happen on an E85, as the DSC system cannot accurately determine wheel speeds etc it affects the power output from the engine, which in turn can sometimes cause an engine fault to be registered.

Thank you very much again! That’s reassuring to know. Sounds like it may indeed be a self fixing model

[Mygreyzedder]

You can get that noise if a brake caliper has been sticking a bit and suddenly frees itself. That account for the codes.

Thanks Mike, I’m happy to hear it’s unlikely to be anything too serious.

[Nictrix]

The 2 may be unrelated. Maybe check your rear springs to see if one has broken.