That seems very odd they all read the same. I'm sure you would get an immediate error if it was a dead short. A weak (say 43k Ω) path to ground may give you a shadow error to look into.

You said all four; do you mean feed and signal on both pre-cat? Or signal on post and pre?

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)