Can You Pass Emissions with Check Engine Light in Colorado?: 1 Minute to Understanding Your Emissions Testing Options

In Colorado, passing an emissions test with the check engine light on is usually not possible. The check engine light, also known as the Malfunction Indicator Lamp (MIL), signals that your vehicle’s onboard diagnostics system has detected a problem related to emissions. During the emissions inspection, technicians connect to the car’s OBD-II system. If the check engine light is illuminated, it is a clear indicator there is at least one emissions-related fault stored or currently happening. According to Colorado’s Air Care Colorado program, your vehicle will automatically fail the emissions inspection if the check engine light is on at the time of testing.

This requirement applies to 1996 and newer vehicles with OBD-II systems. The only exception is if the light is on due to a non-emissions related code—however, that is extremely rare and can only be verified by inspectors. If your car fails, you’ll be provided with a report showing diagnostic trouble codes; you'll need to repair the issue and then retest the vehicle.

As a designer, my approach is always about efficiency and reducing long-term hassle—similar to designing a well-laid out home, it pays to address the root causes rather than conceal problems. If you are prepping for an emissions test and notice the check engine light is on, it's wise to diagnose and resolve the issue early. A good diagnostic scan tool (available at auto parts stores or from a mechanic) will help you identify potential trouble quickly, minimizing repeated trips and delays. Just as in thoughtful interior planning, a little up-front effort saves time and stress later—whether you’re dealing with emissions tests or redesigning your living spaces to be more functional and harmonious. Speaking of optimizing spaces with the right tools, when planning out how a new garage or home office will layout alongside your practical needs, you might explore solutions such as an efficient Home Office Layout to ensure everything has its perfect place.

Tips 1:

Don’t clear the code right before the test—Colorado requires the vehicle to complete a set number of drive cycles before the OBD system shows as “ready.” If you recently reset your check engine light, an “incomplete” status may also result in a failed test. Drive your vehicle as usual for several days after repair to allow readiness monitors to reset.

FAQ

Q: Will my car pass emissions in Colorado with the check engine light on?

A: No, Colorado requires the check engine light to be off to pass the emissions test for most vehicles (1996 and newer).

Q: What should I do if my check engine light is on before the emissions test?

A: Diagnose the cause using an OBD-II scanner or by visiting a mechanic, repair the underlying issue, then make sure the light stays off before returning for a retest.

Q: What happens if my vehicle fails the emissions test due to the check engine light?

A: You’ll receive a diagnostic report and need to make repairs. You can then retest, potentially for free or a reduced fee depending on the county and emissions program policies.

Q: Can I simply turn off the check engine light to pass emissions?

A: Just turning the light off without fixing the problem is not recommended. The system monitors require several drive cycles to show all systems are “ready,” or else the vehicle may be flagged as not testable, resulting in failure.

Q: What is the cost of an emissions retest in Colorado?

A: In many cases, your initial test fee includes one free retest within a certain timeframe (usually 10-30 days depending on the station and locality).