Check engine light came on (code P0138) but disappeared a day later.

Take it back to the dealership and tell them about the problem, maybe the computer-re-flash did not go well.

for this code, you can try this Replace O2 sensor. Repair short to battery voltage in o2 sensor signal circuit.

Hello i would go back to the dealer right away and have them recheck the recall work performed and the re-programing of the computer.HAVE A BLESS DAY from DR.RECO.