There are a number of things that it can be. Another possibility is an extreme lean running condition due to a faulty air mass meter or a large air leak downstream of the air mass meter. You will have a much better picture of what it is after the codes are pulled.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record