Your 164 in a-6 is EGR flow too high, which means a vacuum line problem or the large air hose has a crack and needs to be replaced. No big deal and will not have anything to do with a no start.

I suspect that the battery is at a minimal charge and when you turn the key to posII to check your codes, the cabin fan is running along with the idle air control motor and your battery is then too weak to excite the starter.

Get yourself a trickle charger, either solar or plugin, and get the battery up to a full charge. That usually takes 24 hours.
Then make sure you don't drive around with your headlights "on" all of the time, use the switch to turn them off when not needed. If your alternator is cranking 14.5V and your headlights are using 12V, not enough is being supplied to the battery for a full charge... especially for trips less than 30 minutes.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)