Warning Lights appear and disappear on restart?

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Warrior
Joined: Tue 11 May, 2010 10:02
Posts: 497

  Z3 roadster 3.0i

Warning Lights appear and disappear on restart?

Post by Warrior »

I had a couple of sensors changed last year and all seemed ok, but now, having not driven Zeddie much recently, both the traction control and brake warning lights appear on start up.

Turning the engine off and re-starting makes them disappear.

Is this a code reset issue or something else?
LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 150

  Z3 roadster 2.8

Re: Warning Lights appear and disappear on restart?

Post by LaRy »

Sounds familiar to me. Had the same, and it will get harder and harder, you have to do several restarts.
In my case, the ABS relay in the relaybox became old and had to be changed.
If it is the same as I had, you turn the ignition on, (no fan running, should be quet). When the relay is working, a relay click will come after a couple of seconds, and all warning lights will be gone.
When not working, the relay click will not be there. The relay is rather expensive, so I went to a junkyard and bought an used relay for testing. The Relay will be found in any model of BMW from that time. I had totally different resistance in the relay coil in the not working relay, compared to the working one. If you check the value, I can check mine!

It is so similar, I also changed some ABS sensors, beause the fault code reader said that, but it was the relay. Fake news from the reader :lol:
Warrior
Joined: Tue 11 May, 2010 10:02
Posts: 497

  Z3 roadster 3.0i

Re: Warning Lights appear and disappear on restart?

Post by Warrior »

Thanks LaRy......

I've had ABS sensors, the YAW sensor and brake pedal sensor changed.

Will get the relay checked if it becomes a major issue 8-)
LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 150

  Z3 roadster 2.8

Re: Warning Lights appear and disappear on restart?

Post by LaRy »

What about the "clic" sound when turning ignition on?
Mike Fishwick
Joined: Fri 19 Jun, 2009 10:27
Posts: 2093

  Z3 roadster 2.8
Location: Daglan, France

Re: Warning Lights appear and disappear on restart?

Post by Mike Fishwick »

I find this to be a common thing if the car has not been used for a while - particuarly with an oldish battery. I think that the Slip Control Module, which looks after ABS and ASR operation, is - as a safety system - very sensitive to battery voltage, so that after standing the warning lamps operate, and reset when after a short run the engine is stopped and restarted.
A Z3 is not just for Christmas - it's for life!
LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 150

  Z3 roadster 2.8

Re: Warning Lights appear and disappear on restart?

Post by LaRy »

Mike, maybe we are both right. If the coil in the ABS relay just have poor insulation resulting in wrong resistance, this is of course more sensitive if the battery voltage is low.
When I had this specifc problem I talked to a "whole life" experienced BMW technician. He told me that in certain areas, you cannot trust the fault codes in Z3's. Especially communication from the ABS/ACS unit as it was made from another manufacture and do not communicate to well. That is why you simply can get ABS sensor problems as fake faults. He told me, you have to test the sensors in a traditional way using multi meter.
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