Not passing smog, yet no DTC set... Have all your self-tests passed? A cheap generic scan tool can reveal the status. I like the wireless XTool with iODB tool.
As for flashing... Seems to me like a transmission problem. Mine sets a DTC when it happens but there could be others that don't set. In any case, these won't prevent you from passing smog. They might interrupt the self test however... Probably an intermittent fault with the vehicle speed sensor.
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