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SUM FourC Issues

Help, Advice, Owners' Discussion and DIY Tutorials on the current (third) generation Volvo V70 wagon and XC70 crossover, and second generation S80.

This is a forum for owners or prospective owners of the third generation V70, second generation S80, and its siblings built on the EUCD platform.
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Joined: Wed Mar 27, 2019 9:49 am
Year and Model: 2011
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SUM FourC Issues

Post by RoCo » Wed Mar 27, 2019 10:17 am

I’m new to the forum and need a little help with a tracking down a suspension issue, hoping someone can provide some assitance.
My 2011 XC70 with FourC suspesnion delevoped an issue after I backed into into a very snow covered driveway and left it for the weekend. When I pulled it out I had an “Active Chassis Service Required” and a “headlight failure” message on the dash. The car is also locked into ‘advanced’ suspension mode but rides likes its in ‘comfort+++’ very loose and soft.
After a bit of thinking and digging it seemed like the link between the two systems is the four level sensors. I had a close look at all the connections and wires and everything appeared okay.
I have now purchased a Autel 802 reader and probing the headlight system I get a “Invalid data from SUM Module” which makes sense for a bad level sensor. The 802 can’t seem to access the errors in the SUM system but I can ‘live feed’ data from it. The right front and rear level sensor show zero voltage and do not change while driving. The left appear to work correctly. Also, I'm not seeing any voltage at the body accelaration sensor but I’m not exactly sure how these work or what they do?
The fact the left level sensors work at the right do not leads me to believe that I have a broken sensor power wire between the left and right side. I’m assuming that the sensor power (5v constant) and ground is looped from the SUM, through all relavent sensors and back to ground? If some one can help me understand the wiring path it would really help me localize where to look for potential wire breaks. Or, maybe I’m way off target?
Any help is appreciated. Sorry for the long post.
Cheers, Roco