My check engine light came on while I was starting my car. I diagnosed it through the PCM and it gave me two codes, 0304 and 0407. 0304 is the knock sensor and 0407 is the crankshaft position sensor (reference). Well, I reseted the PCM but the check engine light came on again the next day after a hard start. It seems the problem comes from the hard starts which occurs sometimes in my car. Sometimes it starts immediately after the first crank. Other times, especially in the morning, it needs 2 or 3 cranks b4 starting. I am thinking of checking both sensors to see if they are faulty, but does anyone know how the sensors affect the cranking problems in my car? And if the sensors need to be replaced, how much are they? are they expensive? All opinions and help will be greatly appreciated, thanks! BTW, I drive a 1995 Maxima GXE 5 Speed.

 

REF is for the motor to know where TDC is in its revolution, its very important. Check it as indicated in a Haynes or factory manual. Its an easy change. I dont know for sure but the part should be under $75.