My Issue Was the OEM Battery
Been having odd MIL codes for awhile (year or so) on start that go away after next start (coil/engine light) like the dreaded iced intercooler, except I'm in Las Vegas...everything stock and only items replaced in since 2010 are regular maintenance items as part of the schedule.
This afternoon got ESP Error (TSC light, coil, steering, and engine light) and car would not start at all, engine tries to turn over. VCDS pops steering sensor code/throttle sensor code. Figured I'd try the most simple thing first - the battery.
Stock battery, hasn't been changed since I bought the vehicle brand new 5 years ago....11.84V at rest (after going shopping this morning with approx. 30 minutes of driving) - not good. Guess I should have checked this myself a year ago instead of relying on the dealership's checkup. Looked like battery had been slowly dying and not holding max charge, should be ~12.4V. Took my bad a** car that has never given me issues for 10 years for spirited drive to Autozone and bought a new battery. Put new battery in, ~12.2V; vehicle started up immediately, measuring ~14.2V while running. After a little drive to clear the steering sensor/ESP error, and getting back home, battery at rest measured 12.45V
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My guess is that the start up diagnostics are not happy with a voltage drop from the battery prior to engine start...hence the errors.