Jim Carson One of these things is not like the other

Jim Carson
Emissions check

Because my car is the mechanical-equivalent of a teenager, I have to start the biannual emissions check before renewing my license plate tabs. I knew Subarus had a blanket waiver from the dynamometer test because it effs with the all wheel drive, but I expected an exhaust probe while it idled. Instead, the test consisted of the following:

  1. Person verifying that I had a gas cap and that it was tight.
  2. Corroborated numbers among my license plate, renewal notice, and VIN.
  3. Took my $15.
  4. Technician plugged a handheld computer into the OBDII port on my car.
  5. In response to my surprise that this took less than five seconds, the technician told me Subarus and Volvos have a near-100% pass rate.

InterfaceThe OBDII is required on all cars manufactured after January 1, 1996. It’s supposed to be within three feet of the driver — for example, mine was just left of the underside of the steering column. There are three standards for pin layout and data transfer protocol: GM, Ford and everybody else.

If you’ve ever brought your car in for service because the “check engine” light popped on, the mechanic will ask you “are you sure you put your gas cap on tight?” Upon assent, they’ll plug in a similar computer, query the car, and examine the return codes. A very basic code reader (and MIL-resetter) can be had for $40. If you’re an enthusiast — or Ted — you’ll want the more sophisticated ODB-erator 2000. There are standard diagnostic trouble codes for the powertrain and the controller’s network. Eventually there will be additional standards for the body and chassis. Imagine, your car can rat you out for taking speed bumps at greater than the posted 15mph!


5 Responses to Emissions check

  1. ben c says:

    interestingly, last year when I had my Subaru WRX checked for the first time, they did make me run it for a while (not on the dyno) and I assume they were doing an exhaust check, but I didn’t really look too closely. They never ODB’d my car. I passed anyway.

  2. John says:

    I always have to do the dynamometer for my wife’s car, because she feels like she’ll suddenly “go flying out the back door of the testing place”.

    She used to drive a rotary-engine RX-7. The last time I had that one tested, I ended up in a heated exchange with the tester because he wanted me to go at a relatively low speed in a relatively high gear. The “I’m happier at higher revs” rotary engine coughed and sputtered it’s way to a failing grade. I drove around the block, requested a retest with a different tester, then ran at the correct rpm. Passed.

  3. Lisa says:

    Isn’t it funny how a loose gas cap can cause the lights to come on?

    I will now have to look for that port, just so I know..

  4. Steve says:

    Lisa:
    The loose petrol cap is an issue with cars that run with a pressurised petrol tank. The pressurising is to help push fuel along the fuel line to the engine.

    If the cap is loose, the tank pressure drops (or is non-existent), the fuel pressure to the engine drops, and the engine management system reports that it has a problem.

  5. Pingback: Mechanics | Jim Carson

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