DS5 Cruise Control weird self cancelling

[NotAnInterestingName]

My regular journey from home involves a 40mph limit followed by a 30mph limit, perhaps half a mile from home. I use cruise control set to 42, as I know that this is 40 in reality. When I turn this down to 32 for the 30 limit I find that about half of the time it cancels shortly after. No errors, just the standard message displayed just as if I'd pressed cancel or touched the brake. I've tried resuming it when this happens and it cancels again. It's just like a ghost is pressing the cancel button.

This only ever happens when it's cold and I've just set off. Minutes later I can do exactly the same procedure and it works perfectly and never cancels itself, I've only ever known this to happen in this one place that happens to be on my setting off from home route, shortly after I've set off.

Any clues? Obviously it's cold when this happens, and it's also only started happening since the weather got colder. It's also damp. This is the first year I've owned it, so I don't know whether it's seasonal or a new fault that's happened to appear in the winter.

I haven't tried connecting Diagbox, I will at some point but as I say there are no dash error messages. My limited knowledge made me think about the brake pedal switch - perhaps it thinks I'm touching the brake when I'm not, and pressing it later on somehow fixes it?

[Ross_K]

What's the minimum speed for using cc in the DS5? 25 or 30mph?

[GiveMeABreak]

It's 25 MPH on this model so shouldn't be an issue. Is it an Auto? I was going to suggest that if manual, then the engine speed may be a factor that caused it to disengage if the gear was too high.

There can be other reasons for it to disengage such as ECU detection of a problem, the ABS / ESP ECU or anything else. This is usually one of the first systems to disengage for safety reasons (shame some Teslas don't seem to have the same system when they go off in runaway mode).

[NotAnInterestingName]

Thanks for all the input. 25 is the minimum for cruise in this car, it's an automatic. I'm just using the minus button on the steering wheel to turn it down - press and hold until if gets to 35 then 3 taps down to 32. I do this so often I barely need to look at it.

I drive probably 90% of the time on cruise, most of my driving is on straight and not very busy roads. I basically switch it on then turn it up and down through speed limits or if I end up behind someone else. I must have reduced it from some higher speed hundreds of times without issue, but in this one spot it cancels about half of the time. I'm sure the location is not the issue, unless there's some sort of electromagnetic death ray hidden in a hedge that confuses it. I'm assuming it's more likely that this is the first time I reduce the speed after leaving home, so it's cold or damp somewhere perhaps.

I've also found that when it does do it, if I press the resume button then it usually cancels again a second after. I once managed 3 events in a row but there's a roundabout not long after so I only get limited chances to retry. So whatever event caused the cancellation is ongoing after it happens - possibly ruling out the engine revs theory?

I had a failed brake pedal switch on the Berlingo, but in that case I got a message and a yellow light plus a warning that the cruise control had been disabled, after which it just ignored me pressing anything to try and set or resume it. But perhaps that was a total failure, I suppose it's possible that it may be mostly working but occasionally registering extra presses. I'd hope that if there's a dodgy speed sensor or something then I'd also get messages about the ABS not working?

I was also wondering if it's possible that the minus button is somehow activating the cancel (pause) button next to it, either mechanically or electrically. But the cancellation happens perhaps a second after I've been pressing anything, if I press cancel myself then it happens straight away.

I'll have to try Diagbox and see if anything's been logged silently. All brainwaves gratefully received, this is a very weird one.

[GiveMeABreak]

The other possibility is of course the control switch bank in the left of the steering wheel used to set, suspend and resume cruise. If you use it as often as you say, it may well be starting to wear or causing the odd behaviour.

See what happens when you undertake some live actuation tests with Diagbox. There should be a test you can select from the parameters to test the button pushes. Then watch to see if it registers another push without you doing anything.

[NotAnInterestingName]

Good idea, will have a rummage around and see if I can find some sort of test display. Perhaps a squirt of contact cleaner could be a good idea.

I still can't understand the thing where it only ever happens in the first minutes of a journey but is always 100% perfect after. It's done it about 10 times at this one spot, perhaps 25% of the times I drive there, and has never done it anywhere else.

Its parking place is basically in a field - on concrete but surrounded by long grass all around. So probably as damp as you get outdoors. I'm thinking perhaps there's a spec of condensation on some contacts somewhere that falls off or evaporates after a few minutes. Or perhaps, in the case of the brake switch, gets knocked off when I brake enough.

I may just be patient with this one - I've only had the car since the summer. If it comes and goes with the weather that may be a clue. I'll try to note the weather when it happens, see if a pattern emerges.

[Laythingy59]

My CC switch is worn that badly I can't even set it. doesnt matter if it's warm.
The limiter works so I use this, but noticed this has started going off.
Does anyone know if it's possible to repair, or is it a case of swapping the components?

[GiveMeABreak]

Ok, so on the DS5, there are no stalk type cruise controls, they are integrated into the left and right sides of the steering wheel.

So these are available from Citroen / DS. If you need the part number, please see below:

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[Laythingy59]

Thanks Marc, I actually discovered last night that if I wedge something like a credit card between the speed control unit and the steering wheel at the bottom, my cruise control stays on. I'm going to make something more permenant and see how I get on.

I was trying to see if I could remove the unit all together to inspect it, but couldnt get it off. Does anyone have a guide?

[DS9]

I was going to suggest try using speed limiter instead. I know the OP said he has a light traffic ride but I still like mine a bit more than CC in almost all situations.

The DS9 speedo is very accurate when i compare to what an apps showing such as Waze, just reads a little too high. I set mine to 33/ 44/ 55/ 66/ 77 depending on the speed limit.

One final thing I will say, and I don't know if it's been adopted in newer DS's is the positioning of the CC/ Speed limiter control, and instead of being on the front of the steering wheel itself or on a stalk, its actually a little separate unit behind the steering wheel at the 8 O'clock position. Some of the car reviewers dont like it but after becoming familiar with it to the touch I couldn't think of a better place to put it. i find it absolutely ideal.