Failing an emissions test is rarely a surprise in hindsight. It is almost always one of a short list of causes, and most of them are things you could have known about before you got in line.
Goodyear sits inside Area A, the Phoenix-area emissions zone, which means most vehicles registered here need a passing test before the registration can be renewed. The test itself is performed at state-contracted stations rather than at a repair shop. What a shop does is find out ahead of time whether your vehicle will pass and handle the emissions service needed to get it there.
Who needs a test in the first place?
The Vehicle Emissions Inspection Program is administered by the Arizona Department of Environmental Quality, and it applies in two zones: Area A, covering the greater Phoenix metro across Maricopa County and parts of Pinal County, and Area B, covering the Tucson area.
The general rule for Area A is that a vehicle needs testing if it is model year 1967 or newer and more than five model years old. Most vehicles newer than that are exempt, though an exemption fee typically applies at registration.
Frequency depends on the vehicle. In the Phoenix area, most light-duty vehicles from 1981 and newer test every two years, while 1980 and older vehicles test annually. Gasoline, diesel, flex-fuel, and hybrid vehicles all fall under the program. Fully electric vehicles are exempt, since there are no tailpipe emissions to measure.
A few other situations worth knowing. If you are new to Arizona, your vehicle generally needs to be tested before it can be registered, and Arizona does not accept emissions certificates from other states. If you commute regularly into Area A for work or school, the requirement can apply to you even if you live outside the zone.
Requirements do change, and the details depend on your specific vehicle, so confirm what applies to yours with ADEQ before you plan around it.
The number one reason vehicles fail
If your check engine light is on, you will fail. That is not a judgment call at the test station, it is an automatic result.
On any vehicle from 1996 or newer, the emissions test is largely an electronic one. The station connects to the onboard diagnostics port and reads what the vehicle's own computer reports about its emissions systems. An illuminated check engine light means the computer has already logged a fault in one of those systems, and the test simply confirms it.
This is the part that catches people out. A light that has been on for months, and that the vehicle seems to drive fine with, is still a guaranteed failure. There is no point taking it in and hoping. The fix is to have the codes read and the underlying problem repaired first, which is exactly what diagnostics and emissions service are for.
The trap nobody warns you about: readiness monitors
Here is the failure mode that sends people back a second and third time, and it has nothing to do with whether the vehicle is actually clean.
Your vehicle continuously runs self-tests on its emissions systems. Each of those self-tests is called a readiness monitor, and each one reports as either ready or not ready. The test station needs to see that enough of them have completed. If too many report not ready, the vehicle is rejected. Not failed exactly, but turned away, which costs you the same trip.
Monitors reset to not ready whenever the vehicle's computer loses its stored data. That happens when the battery is disconnected or dies, when codes are cleared with a scan tool, and after certain repairs. A vehicle in that state has to be driven enough for the monitors to run and complete, and that takes a specific mix of driving: cold starts, steady highway speed, and normal stop-and-go, usually over several days and sometimes more than a hundred miles.
So the worst thing you can do is clear a check engine light the day before your test and head straight to the station. The light will be off, the underlying problem may still be there, and the monitors will not be ready. A shop with a scan tool can tell you in minutes whether your monitors are set, which is worth knowing before you make the drive.
What else commonly causes a failure
Beyond the check engine light and monitor readiness, a handful of issues account for most failures.
A loose or failed gas cap. It sounds trivial, and it is one of the more common causes of an evaporative emissions fault. Worth checking before anything else.
Oxygen sensors. A failing sensor sends bad data to the computer, which affects the fuel mixture and can trigger a fault. Sensors are wear items and they do not last forever.
Catalytic converter. The expensive one. A failing converter will not clean the exhaust to standard, and the computer will log it.
Evaporative system leaks. A cracked hose or failed purge valve lets fuel vapor escape and sets a code. In Arizona heat, rubber components crack sooner than they do in milder climates.
Ignition and misfire problems. Worn spark plugs or failing coils cause incomplete combustion, which sends unburned fuel into the exhaust.
Deferred maintenance in general. A dirty air filter, old spark plugs, and overdue oil all push a vehicle toward the edge of its emissions envelope rather than the middle of it.
How to actually pass on the first try
The approach that works is simple: find out before you go.
Have the vehicle scanned ahead of your test. A shop can read stored and pending codes, confirm whether your readiness monitors are set, and tell you what the computer is reporting. If it is clean and the monitors are ready, go take the test. If it is not, you have found the problem on your own schedule rather than in a line.
Address anything the scan turns up, and give the vehicle time to complete its monitors afterward. A repair that clears the computer means starting the readiness clock over, so build that into your timing rather than repairing on Monday and testing on Tuesday.
Keep up with basic maintenance generally. Emissions problems and neglected maintenance overlap heavily, and a vehicle that is current on plugs, filters, and oil is a vehicle that is far more likely to pass without drama.
And go with a warmed-up engine. A vehicle that has been driven fifteen or twenty minutes tests better than one started cold in the parking lot.
Frequently asked questions
Does Goodyear require emissions testing?
Yes. Goodyear is in Maricopa County, which is inside Area A, the Phoenix-area emissions zone. Most vehicles registered here that are model year 1967 or newer and more than five model years old need a passing test before registration renewal. Confirm the specific requirement for your vehicle with ADEQ.
Will I fail with my check engine light on?
Yes, automatically. On 1996 and newer vehicles the test reads the onboard diagnostics system, and an illuminated check engine light means the computer has already logged an emissions-related fault. Have the codes diagnosed and the problem repaired before you test.
Can I just clear the codes before my test?
No, and it usually makes things worse. Clearing codes resets the readiness monitors to not ready, and the station will turn the vehicle away for that. It also does not fix whatever set the code in the first place, so the light typically returns. Repair the problem, then drive the vehicle enough for the monitors to complete before testing.
How long does it take for readiness monitors to reset?
It varies by vehicle and by the mix of driving. Monitors need a range of conditions to run, including cold starts, steady highway speed, and normal city driving, and completing them usually takes several days and sometimes more than a hundred miles. A scan tool can tell you exactly which monitors are still pending rather than guessing.
What should I do if my vehicle already failed?
Bring the report in for emissions service. It identifies what the test found, and a diagnosis will confirm the underlying cause rather than treating the symptom. Once the repair is done, the vehicle needs enough drive time for the monitors to complete before you retest.
Get checked before you get in line
The difference between passing on the first try and making three trips is usually one scan you could have done in advance. Have the vehicle checked, fix what needs fixing, give the monitors time to set, and go once.
Litchfield Auto Repair has served Goodyear since 2013, and our ASE Master technicians work on domestic, European, and Asian vehicles, including hybrid and diesel models. We use professional scan tools to read what your vehicle's computer is actually reporting, and we stand behind our work with a 36-month or 36,000-mile parts and labor warranty on most repairs.
Request an appointment using the button on our home page, and check the current specials before you book. We are at 671 North 137th Avenue, Suite 106 in Goodyear, open Monday through Friday from 7:00 in the morning to 5:00 in the evening. Directions are here if you need them.