D4 cruise control runs away

[harlie]

Hello, we have a 2012 D4 3.0 6speed.
Cruise is odd. Press set and it will show the "cruise setspeed" as the speed when button was pressed (say 90). However the car will pick up and sit on 95. It will stay at 95 if road is dead flat untill you get a section that isn't flat. At this point the car accelerates and just keeps going - like you are holding the +button. Only stops going up when cancel the cruise.

The "cruise setspeed" will still indicate 90 in this example.

I've changed the buttons on the wheel, no difference. The cruise setspeed has me confused as it still indicates the ecu knows it's going too fast.

All 4 wheel sensors are reading true.

It's like the old cruise systems that just had a 2nd throttle cable and the cable is stuck on.

[DiscoJeffster]

I suspect someone what changed the wheel size or region in the CCF to show a true speed thus it’s not aligning to the dash in cruise.

If you have an IID tool or the like you can check.

[Graeme]

Has to be some other issue as it keeps accelerating uphill, presumably well past 95.

I would suspect either the set-speed switch or the clock-spring is faulty, but also possibly the module that interprets the steering wheel switches is faulty.

Might the accelerator be over-riding cruise-control?

[Graeme]

Is the car new to you or you've had it for a while and CC has been OK?

[josh.huber]

If it was switches it would show up on the dash as a speed change, if it was the throttle, would do it all the time and show up as cruise over ride on the dash.

I was over excited one day and calibrated the long accelerometer( I think) in the gap tool. Caused this issue. I think it was in the brake system menu or something. I was looking for the park brake bed in, to many cans.
There is absolutely no information on it. I've always meant to call Cambo about it. But I did it again. Car in neatral flat level driveway. All good after that,
For reference the first time I did it. I was parked on an incline

[DiscoJeffster]

If it was switches it would show up on the dash as a speed change, if it was the throttle, would do it all the time and show up as cruise over ride on the dash.

I was over excited one day and calibrated the long accelerometer( I think) in the gap tool. Caused this issue. I think it was in the brake system menu or something. I was looking for the park brake bed in, to many cans.
There is absolutely no information on it. I've always meant to call Cambo about it. But I did it again. Car in neatral flat level driveway. All good after that,
For reference the first time I did it. I was parked on an incline

That makes a lot of sense. Assuming it behaves like an inclinometer, then it would think it’s hitting a hill and apply more load when it’s not actually needed to maintain speed. Good theory at least.

[harlie]

* we have had the car since 03/2018 (it's my dad's)
* the cruise did work perfectly
* this behaviour started on a long trip, about half way around it started playing up
* the wheel speed seems to line up with the indicated speedo. As this started mid trip, I don't think it's tyre size related

If it was switches it would show up on the dash as a speed change, if it was the throttle, would do it all the time and show up as cruise over ride on the dash.

My thoughts were in line with Graeme which is why I swapped the switch. I only noticed the "set cruisespeed" today and it doesn't change - it stays displaying 90 as the car runs off, this makes me think it's not the buttons or wiring for the buttons - if there was an accelerate signal, the displayed set cruise speed should increase.

I was over excited one day and calibrated the long accelerometer( I think) in the gap tool. Caused this issue. I think it was in the brake system menu or something. I was looking for the park brake bed in, to many cans.
There is absolutely no information on it. I've always meant to call Cambo about it. But I did it again. Car in neatral flat level driveway. All good after that,
For reference the first time I did it. I was parked on an incline

Not really sure what you're referencing here - got anymore info?


On a flat section of road the CC is OK - it settles about 4kph above the indicated set cruisespeed, but it holds steady. As soon as the incline starts it pulls away and continues to pull over the rise and down the other side

[harlie]

ok, after some light reading.

The Longitudinal Accelerometer Sensor is in the Electronic Parking Brake ECU - well worth a try to recalibrate, I will do this tomorrow.

Got me thinking, if this is the cause - wonder if the ECU has been dislodged/moved. Anyone know where the Parking Brake ECU can be found?

edit:
After some more reading, the Longitudinal Accelerometer Sensor is part of the Yaw sensor which is located under the center console next to the EPB switch. Which is interesting as the old man had the Park Brake switch replaced around the time the cruise started playing up (which is awhile ago now)

[Eric SDV6SE]

ok, after some light reading.

The Longitudinal Accelerometer Sensor is in the Electronic Parking Brake ECU - well worth a try to recalibrate, I will do this tomorrow.

Got me thinking, if this is the cause - wonder if the ECU has been dislodged/moved. Anyone know where the Parking Brake ECU can be found?

edit:
After some more reading, the Longitudinal Accelerometer Sensor is part of the Yaw sensor which is located under the center console next to the EPB switch. Which is interesting as the old man had the Park Brake switch replaced around the time the cruise started playing up (which is awhile ago now)

Bet whomever replaced the pb switch has forgotten or plugged something back in wrong.

[josh.huber]

ok, after some light reading.

The Longitudinal Accelerometer Sensor is in the Electronic Parking Brake ECU - well worth a try to recalibrate, I will do this tomorrow.

Got me thinking, if this is the cause - wonder if the ECU has been dislodged/moved. Anyone know where the Parking Brake ECU can be found?

edit:
After some more reading, the Longitudinal Accelerometer Sensor is part of the Yaw sensor which is located under the center console next to the EPB switch. Which is interesting as the old man had the Park Brake switch replaced around the time the cruise started playing up (which is awhile ago now)

Don't rush into re calibrating it, see if it's installed correctly first, I have no idea if my method of calibration is ok or not, I just redid it because I was stupid to do it in the first place, I thought it would step me through some sort of we epb process as my new shoes don't hold.

Mine seems fine now, but that was car on the flat, I let the air bags settle and then did the calibration.