Does a CEL being active matter for mpg?
So back track three months and I had a full exhaust system installed (long tube headers, custom fabricated mid pipe, dual pipes side flared) with a mid pipe that was hand build to fit my truck that included 3 high flow cats (one main, two pre-cats). Anyway once winter hit with colder air my engine has been intermittently throwing the P 0420 CEL code from time to time. Does this effect open/closed loop operation? Hurt MPG?
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