Check engine light came on (code P0138) but disappeared a day later. on 2007 Toyota Corolla

Few months ago due to recall and check engine light the ECM control was replaced by the dealership. Two days ago check engine light came on; when checked it showed the code P0138 but the light disappeared a day later. Please help me with this.

Asked by for the 2007 Toyota Corolla
Take it back to the dealership and tell them about the problem, maybe the computer-re-flash did not go well.
2 more answers
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.