Subaru Legacy GT Wagon, My Dear Check Engine Light


See the cover shot?  That’s me driving at an appropriate speed, assuming the speedometer has a possible 10% margin for error, on the freeway.  At the lower left hand corner, there is a stuck light.  It is one that most people on the road fear most, the dreaded check engine light.  What you don’t see is a blinking cruise control light and an intermittent airbag light.  Most owners would panic.  I don’t.

When I bought the car, it had the check engine light.  I’ve been a car guy my entire life and even went to automotive school just to learn about them, though, I’m not a technician.  I knew enough to feel comfortable with the check engine light to get it fixed later.  After all, it drove perfectly fine.

I’ve taken it to the shop a couple times with a reputable Subaru specialist.  After the first time, the check engine light reappeared after 50 miles.  After the second time, it appeared after 30 miles.  I’m not really all that mad.  I tend to think of automotive repair as a team effort.  I give you the best information I can give you, you do your best to diagnose and repair.

I think that’s fair.

Well, I took my car to a friend’s house today.  He too, is a Subaru owner.  Unlike me, he owns an Impreza WRX STi.  If I remember right, it’s a 2009 model.  Lucky him.

He plugged in his OBD II scanner.  It pulled the same PO171 code.  He connected his lap top to it.  We took it for a short run.  A few things we noted.

1. The MAF was reading at a high level, 3.2g/in.

2. Air/Fuel ratio was right around the ballpark under load.

3. My car was 16* in advance.  I’m pretty sure that has to do with the Techron fuel cleaner I put in it yesterday.

I had a full tank of Chevron gas and the car felt perfectly fine.

Needless to say, I am reasonably comfortable driving it on a daily basis.  I notice slightly late shifts from the transmission, but the engine overall doesn’t have as much pep. The ECU is dumping gas to get the air/fuel ratio right, at the cost of horsepower and gas mileage.

I’m okay with it.  The car still gets 20 miles per gallon on the average.

Still, it’s only a matter of time before I bring it to the same shop.  This time, I’m bringing additional information during the test drive.

I may be okay with a check engine light, but it doesn’t mean I’m that comfortable with it.  It it was running well, the light wouldn’t appear anyway.