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Optical sensor

I don't have one, but thoes 4 codes together are usually signs of a bad injection pump. Gm issued a TSB stating to replace it if those codes are found. Obviously you want to check the wiring and for any air in the fuel. But everytime I see that combination of codes on a customers truck its been a bad pump
if it will start, it usually takes a little bit longer cranking time for it to fire off with one of the two disconnected. do you have a scanner to read if you are getting rpm signal?