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TheBlondeFella

Adaptive Cruise Control - Brake Temperature Error

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Posting here because I just had equally the same issue and surprisingly solution was simple enough.

Fault code:

2093 - Functional Restriction due to Brake Over-Temp

B106F F0 [008] - Unknown Error Elaboration

 

I've found that error occurred just after the tyre change, where I've used 215/55/R17 on Front and 225/45/R17 on Rear wheels. This gives a difference of 4.9% in diameter between front and rear wheels and messes up some brain for ACC system I suppose. Switching back to wheels of the same size, problem is gone.

Confusing thing here is that there are no brake temperature sensors at all. Nothing can go over the temperature. This is really the algorithm issue ending with a weird error, not addressing the issue at all.

Hope this helps.

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@Paulius: Hi. very interesting, thanks for sharing.

 

As you say "I suspect that "there are no brake temperature sensors at all" - so, clearly the error is based on a calculation (the term "elaboration" in the fault message also kind-of supports this hypothesis).

 

My hunch is that the surrogate for actual Brake temperature is measured via the individual wheel speed sensors - the assumption being that as the brakes heat-up, the peripheral wheel speed increases slightly due to metal/rubber expansion. 

 

By using the same principle as is used in the determination of indirect tire pressure (which also doesn't have pressure sensors) individual wheel speeds can be compared to reliably measure slight variations. 

 

225/45-R17 tires are 1.34 inches (34 mm) smaller in diameter than 215/55-R17 tires. My hunch (guess really) is that this may have caused the error - maybe?

Don

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Thanks Don, it all make sense. The tyre difference was ok for determination of indirect tyre pressure, but it may have been too significant for ACC system. So my suggestion is check your tyre sizes when you have similar error.

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I'm using standard sized tyres so I don't think thats the issue for me.

I did do a reasonably gentle 10-15 minute track session the week before and noticed that my rear discs were discoloured blue after. I only had the ESC on sport rather than off so I'm assuming that they got over heated because of that.

Whats weird is that there are no rear heat sensors so I can't figure out why or how I got a brake temperature warning.

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^^^^^ @TheBlondeFella hmm........ I'm not convinced that the calculation of differential wheel speed as a surrogate for temperature should be discounted in your instance.

 

It really all depends on what you mean by  " reasonably gentle 10-15 minute track session". Clearly the blue-ing of the disks suggests a moderately aggressive use of the brakes -so perhaps the same principle was at play - maybe?

 

My suspicion is that the calculation of temperature uses both the aggregated time period between successive brake applications and brake pedal pressure (these are able to be recorded by the controlling module) AND differential in peripheral speed of the individual wheels.

 

Don

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I'm not clever enough to know one way or the other tbh. 😀

 

I'm also not unconvinced that the blue-ing of the rear discs isn't partially because of their quality as I fitted cheap Mtec rears and really know better. 🙃

 

Yes even regular moderate track driving will put more stress on brakes than on the road but I really didn't think I was pushing hard enough to cause an issue. 

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