2009 Subaru Outback CHECK ENGINE LIGHT

FRANKSN

MEMBER
2009 SUBARU OUTBACK
4 CYL
AWD
AUTOMATIC
6,500 MILES

I just bought this car Wednesday. The day before, I took it home on approval and the check engine light was on. I reported it, took it back. They cleared the light and supposedly checked for underlying cause and found nothing. I overheard something to the effect that "it was probably just an overspeed" before it was cleared. I bought the car, drove it onto the freeway in "sport" mode, the light came on again at about 4000rpm. It then went out. Later the same day, on the return trip, the same rpm +/- and the light again, this time it didn't go out. Took the car back today and they have kept it overnight.
My question: What "overspeed"? What should I look for as being a cause? Or is it an impossible question without more info? Thanks.

1 Reply

ZACKMAN

MECHANIC
4,202 POSTS

Overspeed is a condition in which an engine is allowed or forced to turn beyond its design limit. The consequences of running an engine too fast varies by engine type and model and depends upon several factors, chief amongst them the duration of the overspeed and by the speed attained. With some engines even a momentary overspeed can result in greatly reduced engine life or even catastrophic engine failure.

In your case, overspeed is not an issue. Your PCM has a built-in rev limiter that will cut your engine speed from revving too high into the red zone, and a speed governor to limit the maximum speed that you may drive.

At the moment, not knowing the cause for the check engine light, my guess will be as good as yours. If they tell you what code is being recorded by the PCM, you may relay the code to us, and we may help troubleshoot.