connecting OBD causing poor running, traction light, wipers won't turn off and no comms with ecm

[Aeon]

I've noticed twice now, being a technician, working on 2 Volvo convertibles, when I plug in my OBD scanner, the traction light comes on, wipers may turn on, loss of power, and other symptoms.
The symptoms go away when I unplug the OBD connector, and this situation doesn't always happen.
But it's only been on the convertibles out of the plethora of Volvos I've worked on over the last 4 months.
From what I've seen, it may just be a simple cleaning/reseating of the cem contacts.
The customers have never experienced the symptoms I explain, but they don't scan their cars either.

[matthew1]

This needs to be written up in the Journal of Irreproducible Results, unless the journal doesn't consider as irreproducible phenomena results from within a narrow sub-sub-sub type of a car model. viewtopic.php?t=99137

All joking aside, that is very strange. Thanks for the data point, it may help someone down the line, if there is no immediate answer.

[xanthefin]

Measure your scanner OBD Pin pairs
6 & 14
3 & 11

Each pair should not have lower than 120kOhms if there is then yeah it can mess up some like that when connected it drops too much and loses connection. If scanner not have end resistor (can be better then) and shows much higher... i dont have more to comment yet else than it might start sending some data there or keep electrically it high or low preventing the communication like DDoS attack for some reasons.

Another is then if scanner likes use relay jump between those connections is the switching relay okay?
Then the naughty one.. if this is some "higher end" third party scanner tool chinese clone one... they really like to do own schematic and replace chips which makes some tools not work on some situations anymore or with some car brands due reasons xy or z.

Just speculating what might happen there.