Can anyone help me with my problem? Its 02 LS1 with a 3600 yank...I can drive around town for hrs and no issues. As soon as i get on a highway, my ses light will flash and my converter will unlock. i read code and its always P0300. The code wont set, just flashes. Ive checked and replaced plugs (tr55) and replaced O2 sensors. Also, at track, tune says to shift at 6200, but shifting early at around 5500. loosing valuable ET. Car still runs fine and I don't feel a misfire.. Just shitty driving on highway with converter unlocking.

 

Do you have HPTuners or anything? I have read that the smaller mass of the stall can cause the PCM to throw the missfire codes. The only stall experience I have is usually after a cam so I max out the missfire calculation tables anyways.

 

Need a tune for your converter