Would a P0405 OBDII code cause a misfire on cylinder 4? I have a 1999 gmc sonoma highrider 4x4. The P0405 code is Exhaust Gas Recirculation Sensor 'A' Circuit Low. The P0304 code is cylinder 4 misfire detected. I have new spark plugs and wires. New cap and rotor. New fuel injectors. No vacuum leaks. Please help.|||Unless you get a GM mech to answer, all these P codes are pretty worthless. Okay, so you have *something* wrong with your EGR system and a #4 misfire.
You could try having the codes deleted and see what happens. The misfire code may need a certain number of start/run cycles before it clears on it's own if it isn't immediately cleared. That's what I would do ...clear 'em and see if they come back. If they do, then I would bring it to the dealership; they are best equipped for diagnosing these problems.