I changed the crank position sensor on my 2000 chevy tahoe and now the motor turns over but it wont fire. it would start before I replaced sensor

 

Check the connector plug and make sure that none of the wires came loose or broke. Why did you change it if it was running?

 

I PUT THE OLD ONE BACK IN AND IT STARTED. THE REASON I AM CHANGING IT IS BECAUSE THE TRUCK RANDOMLY CUTS OUT LIKE IT RAN OUT OF GAS. I LET IT SIT FOR 30 min to an hr and it restarts. While I was waiting I checked the fuel psi, it was 50 psi. When I checked the codes, p0335, p0336 & one for the knock sensor.