Speed control system faulty / cruise control

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careca
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Speed control system faulty / cruise control

Post by careca »

Hi there, i got a C5 II diesel 2.0 136hp.
Have been having this message about the speed control system, only when i rotate the knob into the cruise control. Normal driving gives no message, nor does the speed limiter, the speed limiter works. Sometimes after a week or a couple of days the cruise control works again with no errors. After reading most of what is available to read in terms of topics related to this issue, most comments pointed me to replacing the 4 pin, 2 contact brake pedal switch. It is a switch that has one normally closed and one normally open contact, i tested them, seemed ok, but i replaced it anyway. I still have the error, last time i connected it to the lexia there were no codes related to it. i was wondering if anyone knows what else beyond the brake pedal switch can be causing this. I am thinking the abs sensors.
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Paul-R
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Re: Speed control system faulty / cruise control

Post by Paul-R »

You say that there were no errors associated with the brake switch but what other errors were there?
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careca
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Re: Speed control system faulty / cruise control

Post by careca »

There was something about the display, can't remember. I will connect the pc again asap and report.
But what would be a common part that disables and controls the cruise control?
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GiveMeABreak
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Re: Speed control system faulty / cruise control

Post by GiveMeABreak »

It may be an intermittent fault, in which case you would need to consult the stored fault codes via Lexia to see what has been logged.
The other issue may be the actual cruise control stalk has worn internally (contact switch).
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Marc
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Re: Speed control system faulty / cruise control

Post by careca »

Hi, i bring news!
After connecting the laptop i observed the following:
- Permanent fault in cdchanger power supply or something, dont care.
- Permanent fault: "pre-post heating relay circuit plugs never supplied" (the car starts normally and right away, what does this mean?)
- Permanent fault: "Brake switch signal Main brake consistency"
Regarding the C1301, the internet says it's either the brake pedal inconsistent signal, or the pressure reading, very common with the ATE MK60 unit.
I did the dynamic readings and the pressure reading was consistent during this time, drove a bit, and pressed the brake pedal when stopped the values were stable.

I cleared the faults and now when i rotate the stalk to the cruise control position it no longer complains of "Speed control system faulty".
I guess that i wrongly assumed that because the cruise control failure did not turn on a warning light permanently, like other errors do, that i could replace the brake switch and check the repair right away, but no, i had to clear the faults in the pc.
I have read somewhere that after some time the car clears it by itself after a certain ammount of time, is that correct?
That would explain why the cruise control seemingly would start to work again without any input by me.

Now i will drive around with the new brake switch and see if the error comes back, if it doesn't, the problem was the brake switch, if it does, the issue is most likely the brake pressure reading.
Makes me wonder why the last 2 times that i got the error, i was driving around, cruise control disabled, but stalk in the enabled position, braking when approaching some kind of roundabout or intersection.
Attachments
plugs.jpg
brake.jpg
c1301.jpg
1632.jpg
2faults.jpg
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GiveMeABreak
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Re: Speed control system faulty / cruise control

Post by GiveMeABreak »

The fault would seem to be with the brake switch - if there is an issue it will disable cruise control. The system will not re-engage until the vehicle ignition is switched off and then on again, as it self-checks. Of course the brake switch is essential to the cruise control system working. It won't affect the limiter though, which is why that continued to work - as this only relies on the accelerator position sensor.

You can ignore the glow plug error - that's a common one, and likely means either the glow plug relay or the plugs are toast. They're not really needed for starting unless in extreme cold - but they do assist with regeneration of the particle filter when required.

Obviously you have some sort of aftermarket audio / bluetooth / Yatour type system connected to the vehicle which the vehicle is complaining about.
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Marc
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Re: Speed control system faulty / cruise control

Post by careca »

Just dropping by to say you were correct,after replacing the switch it started to work again. Thank you.