Xc70 adaptive cruise problem

[Tomthevet]

Hi there. Great to see such an active and well informed forum and hoping to delve into the knowledge! New to Volvo having just acquired a 2013 XC70 which is lovely but having a problem with ACC which I tend to use a lot.
When I got it it said 'cruise control unavailable'if you pressed the button and then instantly gave a message 'cruise control service needed'. When i looked at the dtcs with vida there were loads which when deleted suddenly enabled acc to work but during test drive when acc had been activated for 30s the unavailable message reappeared but nothing else.
Now the dtcs were purely DIM U300044 and FSM U042368 both of which appear to implicate the dash cluster (the old type two clock one). So I guess my question is how often is an acc fault because of the dash cluster when everything else seems to work on the dash, all warning lights etc, no flickering. Is it not kore likely to be a sensor problem?
The red light collision warning seems to work fine as does lane departure warning.
Any help really gratefully received before I think about trying to replace the dash cluster!
T

[BigGreenThing]

Hi there,

An interesting conundrum!

The following link probably relates to P2 platforms, and not specifically the XC70 either, but it does give some good hints. The brake light switch/brake pedal position sensor issue is an interesting one I wouldn't have thought of!

https://www.matthewsvolvosite.com/vo...control-fixes/


It's quite a "young" car to have the DIM fail. And specifically only the ACC. If the DIM had been damaged, it would have been likely (or more likely in my view) to throw more codes/ have a bigger set of fails (e.g. if water got onto it and fried it for instance).

I can only think that it might be either (a) a wiring issue (that might be triggering the DIM fault) or (b) the brake pedal sensor - as the most likely causes. I would also just check al relevant fuses, fuse housing too.

You'd have to google it - but I think there's company that effectively fixes/re-programmes dashboards.

[Lancee]

I am a bit of a layman in this regard, and a little knowledge can be a dangerous thing, but here's a theory.

If the DIM has an issue, I suspect any cruise control activation would be disabled?

I assume the DIM is related to current speed, engine rev's etc and communicates with the cars other modules via the CAN bus. Again any, perhaps not obvious, issue with the DIM could, sensibly, disable the cruise control ?

As you have Vida, perhaps discount any clutch position/switch, brake switch, etc with the live testing facility.

As suggested, I guess you could send the DIM away for assessment/testing/repair, but would need to live without the car in the meantime.

Sounds like an intriguing fault in any case. Wishing you the very best of luck!

[Tomthevet]

Hi all.
Thanks for the input and you guys are thinking along similar lines to me. I think both brake sensors are functioning ok as obviously the brake light comes on via the pedal switch and the servo mounted sensor is giving a nicely linear response as the pedal is pressed.
I think it might come to sending the cluster off though all the companies I've looked at only seem to repair the p2 clusters not p3. One I have seen will transfer all your data to a new used cluster which might be the way ahead assuming it's a hardware issue ?
T

[Lancee]

Do check any clutch position sensor if there is one, of course your car may be an automatic?

[Tomthevet]

Sorry yes automatic.
Cheers
T

[Olaf Els]

It may or may not be relevant, but in my 2010MY XC70 the 'Cruise Control Unavailable' message has only been displayed as a result of dirt or insects on the part of the grille that covers the radar. Cleaning it and spraying it with silicone as a non-stick agent has cured the problem.

I've not checked for codes before doing this, so I have no idea what VIDA would have shown.

[SnineT]

What Olaf said is the 1st port of call.

Before you go deeper though you need to find out where all the sensors and cameras are located. You may have more than just one in the grille and any one of them playing up will cause a fault. Dirt is ACC biggest enemy and if there is a sensor in front of the rear view mirror like newer models even a chip in the wrong place will stop it reading properly. If there's any damage to it or if you can get inside the front camera you may find water ingress is the issue but it's normally they've been knocked out of position. Does the bumper or grille look like they've been damaged or not refitted properly?

Before you start digging the dash about I would highly recommend you scan the car again first. You may find it's nothing to do with the camera sensor and could be an ABS sensor or a whole manner of things. As the car is quite old now it's also possible it just needs re-calibrating, a prior owner might have had the tracking done and this threw it out or lowered the car etc, all these things need considering as the ACC works through many systems rather than just the camera.

[Tomthevet]

Hi all.

All good info but I think if I didn't know how ACC worked and where the sensors were I am pretty sure I wouldn't attempt to fix it without visiting a garage!!
Any sensor problem would show in VIDA which compared to a lot of manufacturer designed DTC software is actually pretty good if people haven't used it before.

Anyway problem solved. As I said before the two codes related to the DIM dash module which is a 2 minute job to remove. Before doing this I released it from its housing and checked part number and ordered a good used one of same number off ebay for £30. This arrived the next day so I disconnected battery, swapped DIM modules, reattached battery and fired it up. The mileage was instantly wrong showing the replacement parts mileage which was very high but when I started the engine this was replaced with the cars actual mileage (must be overwritten by one of the other modules). This remained from then on. Only fault as such was a service indicator appearing which I quickly cancelled as it had just been serviced. And now everything works perfectly, no need to code with VDASH or any other software solution. Was plug and play.

Anyway hopefully help someone with the DIM codes flagging up.
Cheers
T

[apersson850]

Originally Posted by Olaf Els

It may or may not be relevant, but in my 2010MY XC70 the 'Cruise Control Unavailable' message has only been displayed as a result of dirt or insects on the part of the grille that covers the radar.

Where I live the most common reason is that the radar dome is covered by snow.

Try to verify that the radar has not been misaligned. The system can compensate automatically for max 2.5° deviation in alignment.