Replace Sensor ?
 

I have 2008 CTS, 4wd, 129000 miles. Last week the service traction light came on, as did check engine light, with message engine power reduced, but car seemed to run fine. Shut car off, restarted, traction light off, but check engine light remained on. Took to my tech, scanned it, said accelerator position sensor. He erased the code, check engine went out,stayed this way for 2 days. Yesterday the same thing happened. Shut engine off, check engine light stayed on, but within a couple of hours went off, and no recurrence again that day.