what's this fault code actually mean?

[Antti Piirainen]

Douglas Frank wrote:

> 17990  "idle adaptation limit reached"
> 
> ...huh?

This is a poorly educated guess, but it sounds something like the idle 
stabilization system not being able to compensate for excess load at 
idle, poor adjustment or some other cause, ie. it tries to reach the 
desired idle speed, but it has come out of the adjustment range (already 
wide open or closed all the way).

-- 
Antti Piirainen
87 Cq