Dangerous Adaptive cruise control

Joningy

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Hampshire
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MGS5
My 3 week old MGS5 has developed a significant and potentially dangerous problem with the ACC, it doesn't always turn off when pressing the the centre of the 3 left side steering wheel buttons, (the button showing a steering wheel pic)

To set ACC, I'm pressing the left centre steering wheel button, followed by pressing the left steering wheel toggle button to set the speed.

To turn off I press the central of the 3 buttons, or brake pedal.

BUT pressing the centre button on the left side steering wheel doesn't always disengage the cruise control, it keeps going at the set speed, although the screen shows it turned off, ie the light changes from blue to white (I think it's green to white!) {the light is actually blue not green when ACC is activated}
If approaching a junction at perhaps 40 to 60 mph it can be very scary, especially if there is a car in front of me as it keeps trucking on at the previously set speed.

It does eventually turn off, but taking several seconds and not instantly as it should do and sometimes does, it only seems to be a problem over around 30 to 35 mph, below this speed it works as intended (so far)

I contacted the main dealer's service department, I received an unsatisfactory response from them like "we haven't seen many of them yet" NO offer to look into it.
To reiterate, it stops instantly by pressing the brake pedal!

Has anyone else experienced it?
Can anyone explain if I'm not carrying out the correct procedure (can't see this, but it's a new car, my MG4 never gave me a problem)
 
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I normally just tap the footbrake but if your buttons are not working as they should get it in to the dealer.
Hi there @5teep , yes I'll pop in on Monday, we are at the dentist 200 yards away from the Main Penton dealership in Salisbury, it was lunchtime when I rang on Friday, a girl answered the phone and went off to ask someone, they sell Citroen (spit) as well so my guess is, they cover for each other I'll see the main guy at the service desk tomorrow. cheers!
 
I've seen this happen so you are not alone!
Not really a concern to me because if there was any degree of urgency behind disengaging ACC I'd be using the brake pedal regardless.
Just another example of flaky software I expect.
 
Do you see the same behaviour in speed limit mode as well as ACC mode? This will help to indicate if it is a button issue or a software issue.
 
Do you see the same behaviour in speed limit mode as well as ACC mode? This will help to indicate if it is a button issue or a software issue.
Almost certainly a software issue @Anon70 , the button actually deactivates the ACC, well it turns the light from blue (updated colour from green to blue) to white on the driver display, but it takes perhaps 5 or more seconds to switch off, that's way too long for many people to actually deactivate, as I've mentioned braking works as it should, maybe it'll give the dealer a few scratching heads, I'll keep the thread updated as I'm sure it could cause a nasty situation in the wrong hands!
Maybe just a fatory reset will fix it, but MG should know about it.
 
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I don't think it's a button issue because selection works 100% of the time. It's only deselection that has an intermittent glitch.

UPDATE - I visited the main dealer in Penton MG Salisbury yesterday, they were very helpful, neither the sales manager nor the service manager had heard of the ACC problem in mine and @Alb 's MGS5, the car is booked in for an examination next week (21st Oct)

I cannot believe @Alb and me are the only ones with this problem, so I'd suggest other S5 users should try disengaging the ACC by using the button instead of just the brake pedal, but sometimes the button works so it needs doing several times on a journey to check the glitch.

I use 1 pedal driving and wondered if this might be causing the abnormality, but turning it off made no difference.

Further update to follow when I have the results.
 
UPDATE - I visited the main dealer in Penton MG Salisbury yesterday, they were very helpful, neither the sales manager nor the service manager had heard of the ACC problem in mine and @Alb 's MGS5, the car is booked in for an examination next week (21st Oct)

I cannot believe @Alb and me are the only ones with this problem, so I'd suggest other S5 users should try disengaging the ACC by using the button instead of just the brake pedal, but sometimes the button works so it needs doing several times on a journey to check the glitch.

I use 1 pedal driving and wondered if this might be causing the abnormality, but turning it off made no difference.

Further update to follow when I have the results.
UPDATE 2
Wasted half a day yesterday, after dropping off the MGS5 at the MG main dealer, picked up about 2pm, NO CHANGE, the intermittent ACC fault still there.
Unable to talk to the service manager, I was told "I think they've updated a camera"
Will call today, but I think I'll try shouting a bit louder at MG head office, if I can find an email address.
I can cope the same with it as @Alb says by using the brake, but it could cause an accident if someone doesn't react quickly.
 
UPDATE 2
Wasted half a day yesterday, after dropping off the MGS5 at the MG main dealer, picked up about 2pm, NO CHANGE, the intermittent ACC fault still there.
Unable to talk to the service manager, I was told "I think they've updated a camera"
Will call today, but I think I'll try shouting a bit louder at MG head office, if I can find an email address.
I can cope the same with it as @Alb says by using the brake, but it could cause an accident if someone doesn't react quickly.
Shout as much as you like at MG UK head office they have a hearing impairment and dont hear/listen.
An mg4 owner contacted them about a fault, after getting no joy at the dealer, and got a reply saying don't contact us contact the dealer we just sell them the cars.
 
UPDATE 2
Wasted half a day yesterday, after dropping off the MGS5 at the MG main dealer, picked up about 2pm, NO CHANGE, the intermittent ACC fault still there.
Unable to talk to the service manager, I was told "I think they've updated a camera"
Will call today, but I think I'll try shouting a bit louder at MG head office, if I can find an email address.
I can cope the same with it as @Alb says by using the brake, but it could cause an accident if someone doesn't react quickly.
MG's customer service email address is [email protected] include the name and address of your dealer and the registration number of your car.

Unlike @LenEV2016 experience when I contacted them about the amount of time it was taking to sort out the charging problem with my MG4 they contacted my dealer authorising the part replacement almost immediately. Mind you I did accuse them of micro-managing the dealers.
 
Personally, I'd always use the brake tap to disengage the ACC.
I have found slight variation with the way the ACC controls work on my new S5 compared with the MG4.
But....brake pedal tap to disengage, and then press the button later to turn the system off is working for me.

I'll see if the button acts as a disengager switch later today. Must confess I always regarded it as a system on/off button, rather than a disengage switch.
 
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