HELP!! 2003 chevy knock sensor problems

[eleggert]

i have a 2003 Chevy 1500HD. I just had a shop replace the knock sensors on it last week and when he cleared the code it stayed off for maybe 10 miles, so i went back and had him run the codes again and sure enough it was the knock sensor. he told me that he didnt know what was causing it he said he changed both knock sensors and the harness and the intake gasket(he showed me the old one and they were pretty bad) so i called some local gm dealerships and one told me to always do a PCM update but only one dealer told me that and the other one said the same thing the guy at the shop said. I know you are suppose to use OEM knock sensors and a harness and im pretty sure he got the parts from NAPA. I would have done it my self but i didnt want to mess with fuel lines. so any ideas on what i should do or replace i dont really feel like spending $400 again.