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Stroked & Blown · 05-29-2008, 02:12 PM

Is the CEL issue due to the fore (header/manifold) O2 sensor or aft?
The fore 02 controls closed loop fuel trims, the aft sensor tracks catalytic efficiency and has no bearing on fuel trims. If you remove the cat between the two O2 sensors, you can use the non-foulers on the aft sensor without a problem.

Is Porsche using the fore O2 for fuel trims AND precat efficiency?
If so, is this the case for all model years, or just 00-04?

05-29-2008, 02:12 PM	#43
Stroked & Blown Registered User Join Date: Jul 2005 Location: MA Posts: 884	Is the CEL issue due to the fore (header/manifold) O2 sensor or aft? The fore 02 controls closed loop fuel trims, the aft sensor tracks catalytic efficiency and has no bearing on fuel trims. If you remove the cat between the two O2 sensors, you can use the non-foulers on the aft sensor without a problem. Is Porsche using the fore O2 for fuel trims AND precat efficiency? If so, is this the case for all model years, or just 00-04? __________________ 98 Arena Red 986