Yeah, a bad OS could certainly do that. I would not put much faith in the dealer!!

Like JiFaire said, should fill out your signature so we know exactly what you have, any modifications and such.
If OS is still plugged in then try unplugging it. And look for grounds around the back of the engine on passenger side. there should be three, two on top (one on intake, one on water blockoff plate) and one on the back of the engine closer to the filter manager/housing.
The CPS is another connection near the IP, the sensor is down on the timing cover by the crank, but its tail comes up between thermostat and IP.
Have you made sure there is fuel getting to the IP? Do you know if your Lift Pump is pumping fuel? Have you ever drained the water and contaminants out of the filter manager with the T-valve on the thermostat housing?
Have you dumped a lot of Used Motor Oil in the fuel tank, or some other additive? The Optical Sensor must see through the fuel and if it gets dark or bubbly it will throw those codes.
Did dealer change the fuel filter and not put it down in the correct position? It has to be keyed the right way otherwise wont seat and will suck air in, and cause this, and other nonsense sometimes.