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Within the last year I have replaced an O2 sensor, egr valve, and cadillac converter, because of a check engine light. Now about 8 months later my check engine light is back on and I took it to Autozone and they told me it was a dealer code and could not give me specifics except for it was coming from emmissions. Sometimes my car will idle low (500rpms) when I come to a stop and sounds like it might die but never does. My car usually idles at 750 rpms. What could this problem be seeing as though I have pretty much replaced everything with my emmissions? Any help would be greatly appreciated.