Hello: I have a 07 CTS 3.6 W/ 54 k and have had my Eng. light come on twice now the first time last week I had been sitting @ Idle for about 1/2 hr on a slight slope in a parking lot and the light came on shortly after that. the second time today leaving the same lot I think it came on sometime after leaving the lot, coindence? anyone Ideas? I had the codes read after the first time 1 fault P0021, and I had it cleared, the oil was changed between lights it was full and so so clean, the car runs good! any advice? on the second light it was fault code p0009 which the man at Advance told me it was a performance issue, so it was reset again, are these related?

Pat