I recently received both a DTC P0133 and P0153. It seems suspicious that BOTH sensors would go bad at the same time. I monitored the sensors with a scanner while the engine was running and they both hit the 200mV - 400mV range even after clearing the codes. What could cause both of them to go off like that? Prior to the codes coming on, I had replaced the water pump and water pump seal. Could any of this work cause such codes?

 

Sounds like they both got contaminated. Any chance you ran leaded fuel?