Mguard44

I have a friend with a 2004 Chevrolet Silverado extended cab. 5.3L motor. He cannot fuel his truck from the pump without it constantly kicking off. The only effective method anymore is to fill a gas can and then transfer it to the fuel tank. When getting the codes read after the illumination of the check engine light it read both P0442 and P0446. What could this be? Anyway to further diagnose it? Price to fix this? If he fixes 1 code, could the other code go away? Need Help! Thank you in advance.