C5 cruise control error

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Ceenine
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C5 cruise control error

Post by Ceenine »

My problem vehicle has had this problem for 80,000 km/50,000miles. When it passes over a bump or at say 100km/hr along a flat section of road and I accelerate hard and go up a rise, a message “speed control faulty” comes up on screen and the cruise control is no longer operative. It doesn’t occur consistently. When we stop and restart the car we can use the cruise control again with its ecu resetting or some such. I have no errors showing in a Lexia session. Any clues please?

Ps cannot be Carowner virus as it has been misbehaving for at least 5 years.

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GiveMeABreak
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Re: C5 cruise control error

Post by GiveMeABreak »

There can be several causes (I don't know which C5 you are talking about here), but the principles are generally the same:

Any issues with the engine management system will lead to temporary deactivation of speed functions like the cruise and limiter. Consequently, that's why when you switch off the vehicle and then back on again, the system self-checks and if all is ok, off you go again until the fault happens again.

Secondly, and most likely in this case if you don't have an engine system fault code, is that whenever the ABS / ESP ECU is performing an anti skid or trajectory regulation (which you may not even be aware of) then the same applies - the speed control functions are disabled. Given that you seem to be launching the car off into orbit ( :-D ) this could be the reason why. The ESP system may be anticipating a problem as you are taking off up hill and this will be why it is deactivating the system temporarily.

If you try the same manoeuvre at a lower speed, you may find that it does not happen.

Ceenine
Posts: 77
Joined: 17 Nov 2014, 21:21
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Re: C5 cruise control error

Post by Ceenine »

Thanks Marc, I will try launching into orbit at about 80 bkm/h and see what happens. Unfortunately it doesn’t happen consistently which makes it difficult to diagnose and therefore rectify. I will report if I sort the problem for others who are experiencing the same problem.
Don

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GiveMeABreak
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Re: C5 cruise control error

Post by GiveMeABreak »

Try it at the minimum speed you can use cruise control with (circa 30 MPH / 48 KMH) and see if it happens on the same bit of road.