Four-C Service Required + SUM-0023

[Metallo]

Hi Folks,

This is my XC70 AWD - 2006 - 308000 KM

SUM-0023 is the front right suspension acceleration sensor - which I know it is no longer available.

Now, I still have to find out the root cause of the problem, so I plugged in my VIDA and below some screenshots.

1) Is the connector in the image) the right one to measure? I am asking because I get 0 voltage, and you may say, well that is what VIDA shows too, but the fact is that I also tested the one on the left, and I got 0 voltage too.

2) I wonder if the issue is the SUM Module, and that is going to be my next step to see if I get voltage from that. Image attached, looks very clean.

Can you help me to identify which pins I need to measure in the SUM module? I get 12V from the blue and black wires in the gray connector. I cannot interpret what and how to measure the lack of voltage to the connector in the engine bay from the attached schematic.

Thank you!
Alex

[scot850]

Hi Alex. Sorry there has not been any response to your detailed question. Not many owners maintain the 4-C system once it fails due to mainly the cost of the shocks alone.

Personally all I have done with our 06 XC70 is fit a full set of replacement shocks and springs.

It is strange though looking at the live data information on Vida that you are getting only voltage showing at the LR sensor.

Also I don't understand why the information is also showing none of the shocks as calibrated?

As most of the regulars on here know I am not great on the electrical side of stuff. Saying that, I'm hoping that responding may prompt others to chime in.

Thinking about this you are correct the connector is very clean. However it does not mean all is good. Wiring can get damaged and it could have a break internally after the mileage you have on your car.

The fact you are getting voltage on one shock would suggest that the SUM unit is not completely dead, but it does not explain why only one shock is showing data.

I would open the connector (they usually have a sealing gasket in them) and check for corrosion. You must be able to buzz out the wiring for a resistance value and compare with the opposite side. If they are comparable, then it would suggest the 2 sensors are good and the issue is upstream from there.

If I read your location as NB, then on the East coast, I don't know what access to junkyards is like. We occasionally get 05-07 XC70's in the yards here, but nothing presently of that vintage, and therefore no 4C systems.

I know East coast cars are prone to corrosion, but if you need used parts, I'd suggest trying Erie Vo-vo in NYC area, or in Canada there used to be a specialist for Volvo parts in the Toronto area, but I don't recall the name. Finally, on the West coast there is Chapman motors on Vancouver Island. The advantage there is the low use or lack of salt on the roads. They are not cheap but I have not had any bad parts from them.

Thinking about the calibration, it could be it cannot calibrate as the one unit is not functioning.

Neil.

[Metallo]

Hi Neil,

Thank yo for your response.

This morning, I measured for continuity and found the following:

Red at the engine bay connector = Red wire at the green connector that plugs to the SUM

Yellow at the engine bay connector = Brown wire at the green connector that plugs to the SUM

White at the engine bay connector = Black wire at the green connector that plugs to the SUM

I turned the key to position II and measured the output from the SUM between Red and Black wire: 0.033 mV

This tells me that the issue is in the SUM, as I would expect voltage in there, but there isn't.

If that is the issue, then I think I have no chance to replace the SUM because even if I find one, it would be super expensive and needs to be activated by Volvo.

Alex