2013-2019 Cadillac ATS, 2004-2019 CTS, 2004-2016 SRX, 2004-2011 STS and 2013-2019 XTS vehicles equipped with 3.6L, 2.8L, 3.0L engines may exhibit two or more of the following DTCs: P0016, P0017, P0018, P0019, P0008 or P0009.
Check for loose timing chains or tensioners. If no issues are found, the reluctor for the crankshaft sensor that is pressed onto the rear of the crankshaft may have moved. It is possible in some applications to view this with a bore scope through the crank sensor hole without removing the oil pan. GM recommends replacing the crankshaft if the reluctor has moved.
Example of a reluctor that has moved.