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Old 10-18-2000, 07:41 PM   #6
Patrick Olsen
NASIOC Supporter
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
1997 Legacy 2.5GT
1996 Impreza coupe


The check engine light uses inputs from the two O2 sensors - one before the cats, one after (or in between them, I can't remember). If the ECU senses that the cats are not doing their job well enough, then it will turn on the check engine light. As long as you install a good hi-flow cat, and keep the before and after O2 sensors, you should be just fine.

(Or at least that's the way I understand it).

Pat Olsen
'99 Legacy 2.5GT 5speed sedan (RIP)
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