2009 Subaru Forester CEL at highway speeds/passing gear

09 Forester 150k Miles and Remanufactured
engine put on at 135k



Problem I’m trying to resolve: CEL flashes at 75-
80 MPH in passing gear on highway. If I slow
down it will come off and car runs completely
fine. Only happens at the higher speeds.



This is something that has basically been
happening since the new engine was put in.



Last couple months car has been very slow and
low gas mileage and after taking it to different
places we finally had someone say just try to
replace the spark plugs and wires and you’ll be
good. It was a relatively simple job so my dad
and I tackled it ourselves. Come to the
conclusion that spark plugs one and four were
toast so we replaced them all and the car has
been running perfectly. I haven’t needed to go
on the highway recently but went on there today
to test it out and the CEL is still flashing at those
speeds. Car is running perfectly fine (even better
than it did right after the engine was replaced)
other than that.



What could be causing the cel to still come on
even though the car is running like it’s brand
new?!

If anybody else has had this issue or anything
related please lmk how you fixed it!