Cadillac: Northstar code P0171 and P0174, o2 sensors, cadillac dealer

Question
Tom,

I have a 2001 Seville that is setting off two code of lean fuel.  It started at 107,000 miles and runs fine at higher RPM's.  What could be the cause?  I am thinking the O2 sensors on the front and rear exhaust manifolds, but due to the cost (~$100 each), i want to be sure.  What else might I need to check?

Thanks,

Answer
Faulty o2 sensors would cause the CHECK ENGINE light on the dash to illuminate when you are driving the vehicle.

These codes can be caused by fuel pressure, faulty injectors leaking fuel at low speeds.
Faulty computer.

You will need to see your Cadillac dealer as i retired in 2000 and have no reference material to look at.