Peter Blake

Catch a break on auto-emissions testing? Not so fast…

On its face, Senate Bill 257 looks like a good deal.

Starting in 2016, it would give buyers of new cars a seven-year pass before they have to get their first emission test. Currently the new-car exemption lasts only four years.

So you would save $50 — and some time — by skipping two biennial inspections at Envirotest at $25 apiece, right?

As usual, if it sounds too good to be true, it probably is. There is a catch, as you might expect. After the seventh year, your car will be subjected not to the traditional treadmill-tailpipe test (I/M240, in the parlance of the trade) but to a different, harder-to-pass on-board diagnostics (OBD) test.

You are about 50 percent more likely to flunk an OBD test than a treadmill test, according to research by the state’s air pollution control division. And repairs are likely to cost more than they do after a treadmill failure.

icon_op_edA document from the state health department notes that repairs enabling you pass a flunked treadmill test ran to an average $320 in 2011. “However, repair costs for corresponding OBD failures, in other states, have been considerably higher,” it noted.

Two years later, when your car turns nine, you have to take another OBD test. But two years after that, your 11-year-old car would be returned to a biennial treadmill test.

An on-board diagnostic system has been built into every automobile sold in the U.S. since 1996 by federal mandate.

By the way, the bill would apply only to new cars sold in 2016 and thereafter. You do not get the seven-year free ride if you bought a new car in the previous three years.

On the other hand, some older cars will start getting OBD testing in 2016. Vehicles from seven through 11 years old — model years 2006 through2010 — will have to undergo the tougher test. After they’re older than 11, they revert back to treadmill testing.

In short, the financial break given to new car buyers will be paid for by the owners of older cars.

The details of this operation aren’t spelled out in the bill, which makes it difficult to understand.

Doug Decker, mobile sources director in Colorado’s air pollution control division, was asked why the clean-air program was shifting to tougher OBD testing for many cars. “In order to maintain the same air quality benefit of the emissions program, OBD has to fail more cars,” he said.

Hmmmm. So why not do OBD testing for all cars going back to 1996? “Because of the increases in the failure rate,” acknowledged Decker. The older the car, the more likely it is to fail the OBD test. “That puts an undue burden on the owners — at least in the eyes of the Air Quality Control Commission.”

In other words, the issue reflects political realities as much as clean air.

The bill won final passage Thursday 34-0 in the Senate, and should have no problem in the House. It is expected to be given final passage Thursday and should have no trouble in the House. That may be partly because few lawmakers understand all the ramifications.

Why does OBD testing cause more failures than I/M 240? For one thing, if your “check engine” light is on during OBD testing you will flunk. A lit “check engine” light does not automatically flunk your treadmill test.

With a little tampering, it is possible to turn off the “check engine” light and wipe out the effectiveness of your OBD system just before you take a test. Some do it by disconnecting their battery in a certain way. (YouTube, the anarchist’s friend, offers various examples.) If you succeed, the system tells the tester the car is “not ready.” In many states you are then told to come back after a week or two of driving around so that the OBD system is re-established.

But in Colorado, if your OBD system isn’t working, you will simply be shifted over to the treadmill test. Putting up with fraud “is a gamble that we’re going to take,” said Decker. “Sending motorists away and have them come back later — that’s a terrible inconvenience to the motorist.”

The health department predicted overall costs to motorists would go down under the new program, even if repair costs are up 50 percent. That’s because it forecast the OBD testing fee to be $21 instead of the $25 for treadmill. However, the law doesn’t mandate a reduced fee and realistically, nobody expects Envirotest (or an unlikely rival bidder) to drop the fee.

“OBD testing is incredibly stupid,” maintains Donald Stedman, a retired University of Denver professor who specializes in auto emission testing. “It is designed to fail a car when its emissions have deteriorated a tiny bit beyond the federal emission standard when it was new.”

Stedman developed the drive-by RapidScreen program that enables some cars to avoid having to take a treadmill test. You see its 18 vans around town, measuring exhausts at freeway entrance ramps. If you pass RapidScreen twice shortly before you’re due for Envirotest, you don’t have to go in. But you still have to pay the $25.

Shouldn’t RapidScreen alone be able to pick off the relatively few truly bad polluters who cause most of the problem? Stedman thinks so, but Decker argues that a recent experiment showed that polluters pulled in for further treadmill testing often passed the test. “The technology works well to find clean cars but doesn’t work so well finding dirty cars,” he said.

A Yale football coach from long ago once described his job as keeping the alumni “sullen, but not mutinous.” The health department, carefully balancing clean-air goals against repair costs, wants to keep Colorado citizens the same way.

Longtime Rocky Mountain News political columnist Peter Blake now writes Thursdays for Contact him at You may re-publish his work at no charge and without further permission; please give full credit to Peter Blake and

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