Unfortunately, the 1693 is just a companion code. If the 1693 is in the PCU, then it means there is a code present (or past) in the ECU. In other words, the powertrain controller unit is telling you that the engine controller unit has more info to tell you. Most scanners are only able to scan the PCU rather than the ECU. I'm guessing you will see more symptoms down the road. However, I've seen this error before on my truck at high elevations, only to clear up, and then never return (two years now).