FRom a previous pot on this ng:
"In plain English, your engine has a special door inside each manifold
runner (there are four) that restricts the amount of air entering the
cylinder. Above 5,000 RPM, these doors open, admitting more air. Your
engine computer has decided that something has gone wrong with the IMRC
system, and has illuminated the MIL.
That the error code starts with "P1" rather than "P0" means the code is
a
voluntary code that Honda put there without a diktat from the EPA.
Honda
included it as a diagnostics tool.
A P1078 error can be set by a number of things that control the IMRC
system, anything from an IMRC valve that won't hold vacuum to a failed
electrical component. And if the history of such things holds here,
it's
entirely possible you're seeing the error on account of something that
has
nothing at all to do with the IMRC system. This is why the dealer won't
tell you anything. They have to snoop around and do some tests before
deciding on a culprit.
The correct procedure in such cases is to reset the MIL, then just
drive
the car as normal. If the light comes on again with the same error,
then
they get serious about it. A large number of errors are transient and
do
not recur."
Of course, not sure why the SHAWD loight comes on at 4000 RPM.
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