I recently replaced the heater core on my Corolla after is started leaking through the vents of my car. It did get fairly hot but I do not think it "overheated". After performing the heater core repair I started it and drove it around the block. I noticed a hesitation upon acceleration and then a check engine / o/d flash code of 63 about 2 blocks later. This code is supposed to be for solenoid #2 on the transmission. All gears seem to work properly upshifting and downshifting so I am having trouble understanding that code. Before the heater core problem the vehicle ran and drove excellent. I had no drive-ability problems at all. Could anything within the dash cause this type of failure and if not what possible could have gone wrong.