GM changed the chains and tensor but not the guides at 66K miles. P0008 came again at 87K miles. The GM dealer diagnosed that the problem is the reluctor wheel. I took the crankshaft to machine shop and the measurement took was 24.7mm but based on a GM bulletin the measurement of a good Reluctor wheel. should be 25 to 26 mm This measurement is from the end of the machined surface of the crankshaft throw to the edge of the open space in the reluctor. (approximately 3 1/2 teeth). The 0.3mm difference on reluctor wheel could be the reason for P0008 code appear again?.