2015 Jetta Cruise Control Problem

[HowTo]

What is bothersome is that the dealers are taking the cars back instead of just plugging it in to see what the actual error is. Unless they did that and it is a serious one?

They have done more to the others gents car then on mine.
Mine firmware was upgraded that did not do the trick.
What comes to mind from the other gents and myself.

Others:
Steering wheel retrofitted.
Steering wheel replaced.
CC module on steering wheel replaced.
Corrected voltage on some module.
Firmware was upgraded on all 3 cars.

Don't know if this is true. Workshop manager said you cant replace ECU of car due to Vin number? or some sort of board that Vin number plays a important part somehow.

 

[Rouxenator]

The ECU can't just be swapped out because all the devices in the car that communicate with it are coded so they only work with the given ECU, it is standard practice and the idea is to make theft of parts and stripping for parts more difficult.

What I can't understand it why don't they see what error it is. From a driver point of view it is just and error, but the car will log what caused the error to be displayed. Something(s) are returning incorrect values and it can't be that hard to find out what if you look at the diagnostics data.

 

[HowTo]

The ECU can't just be swapped out because all the devices in the car that communicate with it are coded so they only work with the given ECU, it is standard practice and the idea is to make theft of parts and stripping for parts more difficult.

What I can't understand it why don't they see what error it is. From a driver point of view it is just and error, but the car will log what caused the error to be displayed. Something(s) are returning incorrect values and it can't be that hard to find out what if you look at the diagnostics data.

The problem I think it is. The system does not recognize the request you requested.
That is why no error codes are generated.
When the CC does not work, you switch car off and on again. Then fault clears it self. CC works again.

Can you follow signals from various buttons, example CC set button all the way to were it is supposedly ends. (like in a P.L.C.)

 

[Rouxenator]

That would then have been resolved when they replaced the steering wheel as it is the device that acts upon the user request and send the request to what ever unit is responsible for CC. Unless their is a bug in the controller inside the steering wheel.

 

[Archer]

The problem I think it is. The system does not recognize the request you requested.
That is why no error codes are generated.
When the CC does not work, you switch car off and on again. Then fault clears it self. CC works again.

Can you follow signals from various buttons, example CC set button all the way to were it is supposedly ends. (like in a P.L.C.)

Fault will be inactive, but it will still be logged

On a side note, you would be amazed at the amount of data that modern engines can store

 

[Colin62]

Think about this carefully
Wheels skid -> trans output speed will rise. So why the need for sensors on the wheel?
Going too fast downhill? -> Leads to an output to the ABS from engine/trans ECU. Again, no need for additional sensors. I suspect this will only be on adaptive cruise cars, but I can't be sure, I don't have that information available.

I don't disagree with you at all.

But we're not discussing the minimum that you could get away with when designing it yourself, we're discussing what the engineers in Germany decided to use. I know that Merc uses the speed sensors from the front wheels for cruise control, but if any of the reluctance rings on any of the wheels is faulty, cruise control stops working. It's a safety thing - if the speed sensors don't work, ESP doesn't work, and if ESP isn't working, they won't let you use cruise control, no matter what is theoretically feasible. If you have three worn tyres and stick a brand new one on the fourth, it can cause your cruise control to stop working on some models of Merc, as it picks up speed differences between the wheels, and the German's are rather conservative when it comes to safety.

If it was a simple on/off system, it would in all likelihood be working fine. It's not though, it's a new car with a fully integrated system, which will use inputs from various sources not because it needs to but because they are available and it can work better and more safely by using them.

Now if you need adaptive cruise then yes, there will be far more sensory goodness required

I doubt we're talking about a full adaptive cruise control here somehow

 

[Archer]

Well then it all comes down to how they determine vehicle speed, which without access to engine/trans/wiring documents (or the car itself and many many hours ) I wouldn't be able to comment further on what all is interacting with what. But... I would expect other errors to present themselves if wheel sensors are whack (eg speed sensors would likely be used for traction control and ABS as well, which would kick out errors very quickly)

 

[HowTo]

Fault will be inactive, but it will still be logged

On a side note, you would be amazed at the amount of data that modern engines can store

Off note:

I have read this somewhere. Where they say modern cars also have a black box fitted.
This will give indication prior for example accident.

 

[Colin62]

Well then it all comes down to how they determine vehicle speed, which without access to engine/trans/wiring documents (or the car itself and many many hours ) I wouldn't be able to comment further on what all is interacting with what. But... I would expect other errors to present themselves if wheel sensors are whack (eg speed sensors would likely be used for traction control and ABS as well, which would kick out errors very quickly)

Again, I agree with you