recently when I took my truck to have it smog check it failed badly and it was labeled as a gross polluter. So they suggested for me to change my egr valve. I took it to a mechanic and he said he replaced it with a used egr valve. Evrything seems to be running okay. Actually my truck drives perfectly after the replacement. But when I took it to the smog check it won't pass the readiness test, According to them the egr system, oxygen sensor and the catalsyt reads that it's not ready yet. I drove it around for 60 miles and came back and still the same problem. So what happened? What can I do to make it pass smog check? Please help I'm desperate!