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  #1  
Old 07-02-2015, 09:29 AM
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RDC intermittently on orange (not red and tyres all good)

Hi, I have a 2005 4.8is (X5). Intermittently, the flat tyre warning light will come on orange whilst I'm driving. I've had two BMW dealers look at it and they cannot fault the system. I even had one other dealer tell me it won't come on orange whilst driving, only red!!
I've tried new tyres, different pressures and initialising the system multiple times. There is no predicted times it will light up as I've measured distance, fuel levels and times and temps, but nothing is consistent.
I looked at the codes and there is a fault for the ABS and the ride height system - which reset and don't reappear.
I'm no expert but I'm thinking I might have a faulty abs wheel sensor (but I would think it should throw a code for that) or a leaky suspension air bag which is causing the problem, but I can't prove it.
The only thing that appears consistent is that it initially occurs on a freeway when I'm doing a long sweeping right hand curve/turn in the road - hence the leaky airbag theory. Any suggestions? I don't want to spend thousands replacing all the suspension airbags!!
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  #2  
Old 07-02-2015, 11:49 AM
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get your steering angle sensor recalibrated
when you are in a turn the inside wheels turn slower than the outside wheels
which the flat tire monitors as the outside wheels are turning faster and might be losing air, which they are not, it is just the nature of reading wheel speed to gage tire inflation
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Old 07-02-2015, 06:13 PM
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Thanks very much for your advice. I will book it in to get re calibrated.
My only question is wouldn't the indicator think the tyres are going flat and light the indicator red? (I have had a puncture in the past and it indicated red as per the manual).
I'll be interested to see what BMW find when they do the calibration.
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Old 07-04-2015, 04:41 PM
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Chris,

Another thought is the tire pressure you're running does NOT make the front and rear equal each other, so it throws the warning light only on longer than 10 mile trips at HWY speeds. (or will your throw the light all the time after 1 mile?)

As you are aware, the sensors send back a square wave. Any change in the wave pops a light. As the sensors age, get dirty, pick up metal, the signal is weaker and opens an opportunity for a missed square. One quick step is to pull each one and clean the tips off of all metal dust, salt, and sand. They were engineered for a 100K life in all conditions.

On my own 4.8is, it takes two resets attempts to lock in settings. The speed sensors are real sensitive at hwy speeds for reading a difference front to rear. In one case of ABS/Tire sensor fault reading, I discovered a spider web in the teeth of the hub. Removed it and all went back to OK.

What tire pressures are you running front/rear?
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Last edited by StephenVA; 07-04-2015 at 04:50 PM.
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Old 07-05-2015, 09:58 AM
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Thanks for your advice Stephen(?). I have tried all round pressures from 32 to 40 psi with no determinable effect on the occurrence of the fault. I haven't tried different pressures front to rear though. I am happy with a pressure of 38-40 psi for some reason and feel that if I keep this consistent it will at least eliminate one thing.

By the way, the indication is only VERY intermittent. By that I mean it won't occur for months, then it will occur two or three times in a row, then disappear. This is what makes it hard to fault diagnose. I do believe that long right hand curves initiates the fault though. If it was caused by tyre pressure alone or a bad sensor, then I would expect the fault to be more consistent - ie each time I drive the vehicle.

When I replaced the hand brake shoes about six months ago I noticed some small brake pad fragments in the rear left abs ring/cog. The sensor appeared unmarked and didn't appear to have any effect on the occurrence of the indication. I will remove each sensor and give the setup a good clean on each wheel as you advised. By the way the hand brake has never been as good as it was before the shoes were replaced which really annoys me when launching/recovering my boat. But anyway..

I think what bugs me the most is that nobody seems to know what logic will cause the light to come on orange whilst driving. From my readings, I understand it means the system has failed system initialisation, but what is the logic/cause to set the light? If it is just tyre differentials, then the fault should occur every time I drive the vehicle, especially on long right hand curves. Another obvious option is that I have a faulty dash!

On my previous 2001 X5 4.4 I had weird dash indications and figured out it was caused by the ignition switch plug contacts (purple wire pin from memory). After replacing the switch the car ran better! I have been advised the 2005 models don't have the same problem. So whilst it's in getting the steering angle sensor re-calibrated I might change the switch as a precaution given the car has travelled 205,000 kms.

Thanks again for your advice. I will update as things progress.

I find it hard to believe that BMW have never seen this fault before as it either shows their lack of system knowledge and their desire to fix it, or they know what causes it but can't successfully diagnose and repair it. Given the number of X5s in the world, you would think someone would have seen this and narrowed it down.
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