2007 Chevrolet Colorado Trying Find Out Fix Tpm On 2 9 Liter Had Checked They

I am trying to find out how I can fix the tpm on my colorado 2.9 liter ,i have had the tpm checked and they are fine, the tire pressures are fine, the dealer says the relays need to be cleaned, is there a way that i can do this myself and how many are there and where located? the tpm light still comes on telling me its has low tire pressure