‘Check Engine’ Can Lead to Failed Inspection

'Check Engine' Can Lead to Failed Inspection

September 22, 2005 | By Jennifer Saranow

The Wall Street Journal

One of the classic annoyances of car ownership — the check-engine light — is causing a growing number of vehicles to fail inspection.

Traditionally, the light has been a sign that you should get your car checked out sooner rather than later. But now, more states are using it as a signal that a car's emissions system isn't up to par and automatically failing vehicles with an illuminated check-engine light.

That usually means that owners can't register their cars until they pay to get the problem behind their glowing light fixed — even if what's causing the light to go on isn't affecting the car's operations or polluting the air yet, as is often the case.

Most recently, Virginia this month completed rolling out its new emission tests in five northern counties, where drivers of 1996 or newer cars whose check-engine lights are illuminated now fail the inspection. Elsewhere, drivers of 1996 or newer vehicles in the St. Louis area started failing emissions tests in June if their check-engine lights are glowing. They no longer have the option of a backup tailpipe test. New York began rolling out a similar testing program in September 2004 and expanded it in May to nine counties, including the New York City region.

New Hampshire plans to fail such drivers starting in May, and Ohio put into place a comparable policy last year. Other states that have implemented similar programs in recent years include Louisiana, Maine and Vermont.

The Environmental Protection Agency estimates about 33 states plus the District of Columbia now have some kind of emissions testing in place that involves looking at whether the check engine light is on.

This growing emphasis on the check-engine light, technically called the "MIL" or "malfunction indicator light," comes as there's more chance a car's illuminator will be lighted. In the past, the light was more of a reminder that vehicle maintenance was needed, and was based on a simple computer system that monitored basic engine-control components.

But the Clean Air Act Amendments of 1990 mandated that manufacturers equip all light-duty cars and trucks from model year 1996 on with a more sophisticated "on-board" computer system that more closely monitors engine-transmission and emissions systems and better identifies problems that could lead the vehicle to pollute the air.

The new on-board computer comes with many more sensors than its predecessor, so that it can pick up potential emission-related problems as small as a loose gas cap (registered as a vapor leakage) and as big as a broken catalytic converter, the primary device that cleans up a vehicle's emissions. If it detects a problem, it displays a glowing picture of an engine or the words "check engine" or "service engine soon."

"Virtually anything in the car that has even a little bit of an effect on emissions can set off the light," says Paul Baltusis, on-board diagnostics technical leader at Ford Motor Co. Other examples of what can set off the light, he says, include engine misfire and broken wires and sensors. Meanwhile, mechanics say they have seen lights set off by problems varying from gas-covered gas caps to, more rarely, problems with the wiring of computers running parts such as power windows.

The amendments to the Clean Air Act in 1990 also mandated that states with areas that didn't meet certain air-quality standards incorporate more-advanced emissions tests involving the new computer systems, called "On-Board Diagnostics II," or OBD II systems, into their vehicle emissions-testing programs for 1996 and newer vehicles.

Generally, if consumers have an illuminated check-engine light when their inspection time comes around or fail an emissions test because of a lighted indicator, they have to get the car fixed and the light turned off before they can register their car or in some states, obtain a sticker necessary to avoid possible tickets and fines, even if what is setting their light off is relatively minor.