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Electronic Parking Brake and ACC fault

28K views 59 replies 10 participants last post by  twist 
#1 ·
Fault occurred 3 weeks ago eventually got in to our local dealer as no loan cars available until this week.
Car was in 2 days due to new switch required.
Partner drove home within 15mins, fault reoccurred.
Rang local dealer service dept as needed the car to go away this weekend, car booked back in today.
Partner waited 3 hours for the car and still not resolved.
Now being told no appointments available now till 18th August and booked in for a further 2 days and no loan car available.
Not happy :-( :-(
 
#2 ·
What are the fault symptoms you are experiencing ?

Not aware of how the parking brake would be related to the ACC. Is it 2 separate faults you have ?
 
G
#3 ·
Impala said:
What are the fault symptoms you are experiencing ?

Not aware of how the parking brake would be related to the ACC. Is it 2 separate faults you have ?
The electric parking brake is mentioned in the ACC control module so must have some input or might be operated by that module?
 
#5 ·
Only a suggestion but if there is a brake fault the ACC won't activate .
ACC needs control of the braking system to slow the car down when nessesary so if there is a brake fault the ACC identifies it and will override any commands from the driver.
So ACC is doing its job and probably not faulty.
Poor from VW they should prioritise braking problems and know how to fix their own cars first time.
 
#6 ·
Clubchamp98 said:
Only a suggestion but if there is a brake fault the ACC won't activate .
ACC needs control of the braking system to slow the car down when nessesary so if there is a brake fault the ACC identifies it and will override any commands from the driver.
So ACC is doing its job and probably not faulty.
Poor from VW they should prioritise braking problems and know how to fix their own cars first time.
I'd understand if it was a footbrake problem but I'm not sure why the handbrake has anything to do with it. I suppose if you don't use Auto Hold but you do use ACC and it came to a complete stop behind another car, it may need to apply the handbrake rather than keeping the footbrake held. So maybe it's just being cautious and only allowing ACC to work if all possible scenarios are covered.
 
G
#9 ·
TM2019 said:
Im more disappointed in the time to resolve and not even been offered a loan car while its in.
Used to have a fiat bravo many moons ago and they were willing to give me a car everytime but I had to pay for the insurance £21 be it for one day or seven, needless to say I didn't take it.
Possibly a deliberate ploy at that time?
 
#11 ·
twist said:
Clubchamp98 said:
Only a suggestion but if there is a brake fault the ACC won't activate .
ACC needs control of the braking system to slow the car down when nessesary so if there is a brake fault the ACC identifies it and will override any commands from the driver.
So ACC is doing its job and probably not faulty.
Poor from VW they should prioritise braking problems and know how to fix their own cars first time.
I'd understand if it was a footbrake problem but I'm not sure why the handbrake has anything to do with it. I suppose if you don't use Auto Hold but you do use ACC and it came to a complete stop behind another car, it may need to apply the handbrake rather than keeping the footbrake held. So maybe it's just being cautious and only allowing ACC to work if all possible scenarios are covered.
I think if there is any issue whatsoever with the braking system the ACC will not activate .
To the OP is there a warning light for ACC or just the brake.
 
#13 ·
vernerbongo2 said:
Impala said:
What are the fault symptoms you are experiencing ?

Not aware of how the parking brake would be related to the ACC. Is it 2 separate faults you have ?
The electric parking brake is mentioned in the ACC control module so must have some input or might be operated by that module?
Only in the sense that the ACC can bring the car to a complete halt behind a vehicle in front, and will engage the brake until the other car moves off and the ACC auto resumes.
 
G
#14 ·
Impala said:
vernerbongo2 said:
Impala said:
What are the fault symptoms you are experiencing ?

Not aware of how the parking brake would be related to the ACC. Is it 2 separate faults you have ?
The electric parking brake is mentioned in the ACC control module so must have some input or might be operated by that module?
Only in the sense that the ACC can bring the car to a complete halt behind a vehicle in front, and will engage the brake until the other car moves off and the ACC auto resumes.
I'm not overly technically minded and the technology in cars these days is very advanced.
I've never thought about how much goes into building a car until this forum, looking at parts diagrams there are litterally hundreds of thousands of parts in a car and then when you go into the module programming side of things it's the same :shock: :p
 
#15 ·
Impala said:
Only in the sense that the ACC can bring the car to a complete halt behind a vehicle in front, and will engage the brake until the other car moves off and the ACC auto resumes.
Never been able to simulate this implied auto condition, when using ACC where the car stops behind another car when the car moves off automatically.
Ours will just sit there until the accelerator is "touched" then off it goes in 1st gear at an alarming ,"must catch up" acceleration.
Frightens the wife so much she will not allow the car to stop in ACC and turns it off in stop/start traffic. :!:
So the question is - Should it / does it / move off without any driver intervention whilst in ACC?
 
#17 ·
brid said:
Impala said:
Only in the sense that the ACC can bring the car to a complete halt behind a vehicle in front, and will engage the brake until the other car moves off and the ACC auto resumes.
Never been able to simulate this implied auto condition, when using ACC where the car stops behind another car when the car moves off automatically.
Ours will just sit there until the accelerator is "touched" then off it goes in 1st gear at an alarming ,"must catch up" acceleration.
Frightens the wife so much she will not allow the car to stop in ACC and turns it off in stop/start traffic. :!:
So the question is - Should it / does it / move off without any driver intervention whilst in ACC?
It should but there's only a very brief window where the system will allow the car to move automatically from stationary if the car in front moves (I think it's about 3 to 5 seconds). It should show a message on the dash that says something like "ACC ready" and if that disappears, it will not move off automatically when the car in front moves off.

After that, you either push the accelerator *or* you can hit the "Res" button on the steering wheel. However I find that the Res button doesn't work every time and I end up having to press the accelerator slightly.

As for the "lurch" I know exactly what you mean. But you can soften that a bit by going to Individual mode (with the Mode button on the center console) and setting ACC to "comfort". It's not heaps better but it's less like the car thinks it's in a drag race :)
 
#18 ·
brid said:
Impala said:
Only in the sense that the ACC can bring the car to a complete halt behind a vehicle in front, and will engage the brake until the other car moves off and the ACC auto resumes.
Never been able to simulate this implied auto condition, when using ACC where the car stops behind another car when the car moves off automatically.
Ours will just sit there until the accelerator is "touched" then off it goes in 1st gear at an alarming ,"must catch up" acceleration.
Frightens the wife so much she will not allow the car to stop in ACC and turns it off in stop/start traffic. :!:
So the question is - Should it / does it / move off without any driver intervention whilst in ACC?
Mine does exactly that.
Stops on its own, when car in front pulls away mine starts up and follows.
If yours dosnt there is something wrong.
Having said that you need a lot of faith in the system ,and any touch on the brake pedal disengages the ACC.

In normal driving ( not ACC ) does your engine start up on its own in start/ stop mode When the car in front pulls away .?
It should with no input from the driver.
 
#19 ·
Just had a thought and new to this forum (Still waiting for car ). Is this problem anything to do with Traffic jam assist?
 
#20 ·
htpeargo said:
Just had a thought and new to this forum (Still waiting for car ). Is this problem anything to do with Traffic jam assist?
I suspect VW are talking bollocks as usual in the brochure. The "driver assistance pack plus" only adds blind spot monitoring. I'm pretty sure Traffic Jam Assist is just a part of ACC and is included regardless of the options you choose so every T-Roc should have it (except I guess it works slightly different in a manual car).

Maybe someone who has a DSG model but NOT the extra assistance pack can clarify if their car is still happy to trundle along automatically with ACC at under 40mph?
 
#21 ·
Clubchamp98 said:
Mine does exactly that.
Stops on its own, when car in front pulls away mine starts up and follows.
If yours dosnt there is something wrong.
Having said that you need a lot of faith in the system ,and any touch on the brake pedal disengages the ACC.

In normal driving ( not ACC ) does your engine start up on its own in start/ stop mode When the car in front pulls away .?
It should with no input from the driver.
If the "auto engine stop start" is disabled or the engine remains running at the time of self stopping does the car still move off unassisted?
Normally I run with auto stop start disabled when in town centre but when I keep stop/start active I have not really taken much notice, perhaps it does but always thought that this was due to either a slight turn of the wheel or the removal of the foot from the brake pedal. (DSG)
Never associated this with the car in front moving off. Must pay more attention.
 
#22 ·
brid said:
Clubchamp98 said:
Mine does exactly that.
Stops on its own, when car in front pulls away mine starts up and follows.
If yours dosnt there is something wrong.
Having said that you need a lot of faith in the system ,and any touch on the brake pedal disengages the ACC.

In normal driving ( not ACC ) does your engine start up on its own in start/ stop mode When the car in front pulls away .?
It should with no input from the driver.
If the "auto engine stop start" is disabled or the engine remains running at the time of self stopping does the car still move off unassisted?
Normally I run with auto stop start disabled when in town centre but when I keep stop/start active I have not really taken much notice, perhaps it does but always thought that this was due to either a slight turn of the wheel or the removal of the foot from the brake pedal. (DSG)
Never associated this with the car in front moving off. Must pay more attention.
Interesting reading all the different experiences with ACC and Start/Stop.

In my view, both these systems work best with a DSG and I suppose that is what they are really designed for and it is perhaps to VW credit that they have been made to work to a limited degree with a manual gearbox. This really hightlights the lack of detail and explanation in the Owner's Manual, as the differences and limitations with a manual box are not discribed.

My car is a DSG and I very seldom ever have to turn anything on or off - I drive with Auto Hold and Stop/Start permanently ON. I occasionally cancel Auto-Hold when I pull out from a T-Junction on a hill, as it avoids front wheel spin that can happen when reving hard to release Auto Hold while turning a 90-degree corner.

When I use ACC, I never need to touch anything unless I want more/personal control, such as pressing Cancel and cruising in 'Reduce speed now' zones rather than pressing the brake pedal. The car is quite happy running on ACC at reducing speeds to a complete halt behind another car. NOTE: the stationary car must have been in range of the ACC before it came to a standstill, and you cannot automatically slow and stop behind a car which has been sitting stationary before you arrived.

As Twist mentioned, the ACC will auto resume operates for a short while after stopping. Resuming without the auto feature can best be achieved on a DSG by either light pressure on the throttle or by slight turning of the steering wheel. This is also a way of restarting the engine when Stop/Start has activated, but restart is also automatic if a stationary car in front moves off.

If you apply the foot brake at any point and for even the briefest of time, then ACC will be cancelled, but the previously set speed will still be stored and can be re-activated by pressing Res(ume) on the steering wheel.
 
G
#23 ·
A Manual gearbox isn't any use in the scenarios mentioned in all the comments.
Not much use when you have to change down the gears yourself, otherwise it can work but not worth the effort.
Definitely takes a lot of faith sitting back and trusting the technology :p
 
#24 ·
brid said:
Clubchamp98 said:
Mine does exactly that.
Stops on its own, when car in front pulls away mine starts up and follows.
If yours dosnt there is something wrong.
Having said that you need a lot of faith in the system ,and any touch on the brake pedal disengages the ACC.

In normal driving ( not ACC ) does your engine start up on its own in start/ stop mode When the car in front pulls away .?
It should with no input from the driver.
If the "auto engine stop start" is disabled or the engine remains running at the time of self stopping does the car still move off unassisted?
Normally I run with auto stop start disabled when in town centre but when I keep stop/start active I have not really taken much notice, perhaps it does but always thought that this was due to either a slight turn of the wheel or the removal of the foot from the brake pedal. (DSG)
Never associated this with the car in front moving off. Must pay more attention.
It should do all features of ACC are active , the start stop system is separate from ACC.
Once the engine has stopped in start/ stop And auto hold mode taking your foot off the brakes won't do anything in a DSG.
Turning the wheel or slight pressure on accelerator will start the engine.
So will the car in front pulling away.
 
#25 ·
Clubchamp98 said:
It should do all features of ACC are active , the start stop system is separate from ACC.
Once the engine has stopped in start/ stop And auto hold mode taking your foot off the brakes won't do anything in a DSG.
Turning the wheel or slight pressure on accelerator will start the engine.
So will the car in front pulling away.
Now maybe we come to the crunch. "All features active" Just what are all the features.
Never use the auto hold feature in general as it is too restrictive at busy roundabouts etc:
Is this part of the features and must it be active to facilitate this "auto move off" ?
 
#26 ·
brid said:
Clubchamp98 said:
It should do all features of ACC are active , the start stop system is separate from ACC.
Once the engine has stopped in start/ stop And auto hold mode taking your foot off the brakes won't do anything in a DSG.
Turning the wheel or slight pressure on accelerator will start the engine.
So will the car in front pulling away.
Now maybe we come to the crunch. "All features active" Just what are all the features.
Never use the auto hold feature in general as it is too restrictive at busy roundabouts etc:
Is this part of the features and must it be active to facilitate this "auto move off" ?
I think for the ACC to work properly the auto hold probably needs to be on.
It's the start stop I don't like at roundabouts it cuts the engine before you come to a halt and won't let you just creep to the junction lines.
But ACC is no good at roundabouts as if it loses the car in front it will accelerate again.
You need a lot of faith in ACC and I only use it on the motorways now.
 
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