Friday, September 10, 2010

That darn "Check Engine" light.

Today we're discussing that light that sometimes pops up on your dash. "Check Engine", "Service Engine Soon", just a yellow picture of an engine, it's all the same thing. What it is, since 1995's OBDII standard came into play for all vehicles sold in North America (And most of the world) is technically called the Malfunction Indicator Lamp, or MIL.

The MIL comes on when your engine computer (ECM or PCM, depending who you ask) stores what is called a Fault Code. Fault codes are triggered for a number of reasons, running the spectrum from a single cylinder misfiring to a temperature sensor reading an unusual value to your gas cap being loose.

One major flaw in the OBDII system is that all you, the driver, have is that one light. A lot of people get trained by their mechanics that "It's no big deal, just ignore it", when sometimes there can be a new, underlying issue that needs more immediate attention! Living with your light on all the time can be very dangerous to your wallet - unless you're constantly able to have it scanned to make sure, you can't possibly know that there aren't any newer, more troublesome codes in there!

Code Readers

Diagnosing a check engine light can be a tricky thing for people who, as they say, "Know just enough to be dangerous". Buying a $60 code-reader is definitely helpful, but here's the problem. You plug in your code reader and find out that one of your codes is P0125, which indicates that the coolant temperature sensor is reading too low for closed-loop fuel control. So you've spent $60 to find this out, but what do you do with it? (Hint: Ask someone like me) You don't know if the sensor is reading correctly or not. You don't know if the coolant if actually too cold or not. You don't, really, know much more than you did before. This brings me to my next point:

Why diagnostics are so expensive!

Many shops charge more for diagnostic labour than mechanical labour, and there's a reason for that - a trained technician knows how to use their time properly and diagnose the root cause of your MIL properly. A good, multi-platform scantool costs thousands of dollars and has to be updated each model year, along with the tech's knowledge, to keep everyone abreast with the latest technologies and procedures. Scanners allow a tech to sit in your car and watch data from all sensors live, as well as to trigger self-tests that aren't necessarily run continuously as the car drives, but which can also trigger an MIL.

So what should I, Average Driver Person, do?

My advice?
  • Get a code-reader, or borrow a friend's, but don't rely on it.
  • Use resources like this blog when you're not sure if your problem calls for further diagnosis, research or can just be ignored for the time being.
  • If you do need further diagnosis, find a good shop with technicians who keep up on their training and equipment! In the US, this means ASE certification at the very least. (ASE isn't the best, but it's all you seem to have down there). In Canada, a recent grad from an Auto Service Tech program with a recent Class S license has had great training.
  • Drive happy!