Cruise Control Malfunction: Causes & Fixes

Hello!

"On my 2001 T4 2.5 TDI ACV, I've been experiencing a small, relatively insignificant problem for some time now, but I still want to fix it."

The cruise control is forgetting the set speed. There are no error messages or entries.

You're driving comfortably at 100 km/h on the highway, then accelerate for a stretch of 10 km to 160 km/h, and want to let the bus slow down back to 100 km/h before the next 100 km mark, but the cruise control seems to have forgotten the initial setting, so you have to manually set it to 100 km/h again using the "SET" button. All other functions of the cruise control are working normally.

However, I have never been able to activate the brake or clutch, and I've tried it multiple times. It doesn't seem to remember the set value, but why?

I would like to fix this issue because I am currently installing a Multifunction Lever (MFL) in my T4, and everything should fit properly beforehand. Also, regarding the MFL, does anyone happen to have the pinout for the T4h connector (on the steering column), specifying which pins are for SET, on/off, Cancel, and +/-? There is no "Cancel" function in a bus, but I am implementing it using the clutch contact.

Best regards,

Peter.

After a certain period of time, the intention is for the cruise control system to forget the previously set speed.
It's also stated in the instructions.

Hello Michi!

After just a few minutes? I very often drive on a highway section with many tunnels where a speed limit of 100 km/h applies, so there's always acceleration in between, and then you reach the speed limit before the next tunnel. This has worked perfectly for over 6 years now, and it's no longer working... that's why I'm surprised .

Greetings,

Peter.

Mc_Givertechnik wrote:

After just a few minutes?

I don't know what the instructions say, but according to the T4 wiki, the memory is cleared after 5 minutes if the speed difference between the current and stored speeds exceeds 10 km/h.


Greetings,
Michael (also known as Cali in the T4 forum ).

Hello Michi!

That would explain a lot, but I don't quite understand why I didn't notice it before. I will stop next time when I am driving .

Regards, Peter.

Okay, so my ACV (see signature) definitely doesn't forget the value. I can set it to, for example, 50 km/h, drive 30 or however many kilometers, and when I press RES, it goes back to 50 km/h. It only loses the value once the ignition has been turned off.

In my opinion, the question was phrased in a way that implied a request for faster acceleration using the gas pedal after experiencing forgetfulness. And it's precisely here that your ACV (Adaptive Cruise Control) exhibits a form of amnesia.

If you set the cruise control to 100 km/h and then accelerate to over 110 km/h within a period of 5 minutes, the cruise control will be deactivated. While the previously set speed of 100 km/h can still be accessed, it is no longer active.

Uwe wrote:

The previously set speed of 100 km/h is still accessible, but it is no longer active.

Okay. But as I understand it, that's not his problem. His problem is that he can't retrieve the speed setting even by pressing the RES button. And that's not how it's supposed to work.

Where did he write that?

Sure, here's the translation of the German text into English:

"There:"

Mc_Givertechnik wrote:

. You're driving comfortably at 100 km/h on the highway, then you accelerate for 10 km to 160 km/h, and want to let your bus slow down back to 100 km/h before the next 100 km stretch, but the cruise control has forgotten this setting, so you have to manually set it to 100 again using the "SET" button.

If I do this on my device, do I just need to press the "RES" button, and will it go back to 100 km/h?

I see it the same way as Uwe; both my Golf and my T5 automatically resume their set speed after overtaking maneuvers, without me having to press anything. Whether I press the "Set" or "Reset" button is irrelevant. With the Golf, I know that it remembers the setting for a very long time, which has surprised me before. As for the T5, I can't say much because I always use cruise control on the highway, and only accelerate briefly for short overtaking maneuvers. That works perfectly fine.

Ah, it seems I haven't provided enough information.

It has always been the case, at least so far, that my adaptive cruise control (ACC) maintains the set speed and resumes that speed value as soon as you release the accelerator pedal, regardless of how long or fast you have been driving.

Yes, my ACC also doesn't follow the last saved value when you press the RES button; it definitely forgets it. So, you have to manually adjust the speed using the pedals and then save it with the SET button.

As I said, it hasn't been an issue so far.

Regards, Peter.