This article is to share our knowledge and experience with emissions testing in Atlanta, Georgia and the surrounding 13 counties. Yes, you can pass emissions with a tune.

To pass the emissions inspection your check engine light must be off, and all emissions monitors must report as “ready” or “set.”  You can check the monitors yourself if you buy an OBD2 scan tool. This is also handy to check trouble codes and confirm certain sensors are working properly. The Autel AL319 is about $30 on Amazon and the Hyper Tough HT300 is $40 at Walmart. They will get the job done. For something a bit nicer, the Zurich ZR8 for $100 from Harbor Freight is a decent choice.

Notice the green checks on the screen of the scan tool below. Each brand of scan tool is slightly different but the basics are the same. Most will have a menu or I/M button to bring you directly to this screen. Each green check is for an emissions monitor that the ECU has tested and passed, and all monitors but one need to have a green check to pass emissions here in Georgia. You are allowed one monitor to be “not ready” and as long as you don’t have a check engine light you will pass. Any grayed-out items are things your vehicle doesn’t have, so don’t worry about them.

Anytime you clear a check engine light, read a calibration off an ECU, or flash a tune to an engine computer, it will reset all of the emissions monitors – this scanner above would show all of them as a red ❌. Again, different scanners show this slightly different ways, but basically green is a monitor that has passed and is ready, red is a monitor that hasn’t passed yet. Lastly, this emissions monitor function is different than the check engine light or trouble code features of your engine computer, so don’t get them confused. You can have all red ❌ for your monitors and no check engine light. The engine computer uses the monitors to keep track of the health of the emissions systems over a long time like days, weeks, or even years. In contrast, a check engine light is triggered immediately after a fault. 

How do you get the red monitors to change to green? You will need to perform one or more drive cycles. More on that below. 

One other thing, in Georgia (and most other states) there is a visual inspection requirement. They are checking for catalytic converters. So, if your car doesn’t have them, it’s an automatic failure. If the check engine light is on, that’s also an automatic failure. 

We want to be very clear that if you bring your vehicle to us and we read out the tune file in the ECU or we flash a tune on it, the emissions readiness system monitors will be reset. So, if your tag expires next month, you should take care of the renewal before bringing us your vehicle.

This does not mean that our tuning service will prevent you from passing emissions. We have numerous happy customers with heavily modified vehicles that comply with and pass emissions each year. Rather, understand that as you modify components (including the tune calibration) of a vehicle it may impact the speed of the results of the emissions readiness system. 

The normal driving of your vehicle after you reflash a new tune calibration should eventually get all of the monitors to go back to “green”, but we have no way to control that all of the drive cycle requirements are bring met, or how long it takes to meet them, and no refunds or additional labor will be provided to set emissions monitors or get a vehicle ready to pass emissions. 

Understanding Emissions Readiness:

Emissions readiness involves a series of self-tests run by the engine control module to ensure all emissions systems are working correctly. If there’s an issue, it alerts the driver via a diagnostic trouble code (DTC) or check engine light (CEL). Each test is called a readiness monitor or simply “monitor.” These monitors run continuously as you drive, but some require specific conditions to operate. 

After installing a tune, all monitors will be reset to “incomplete” or “not ready.” This doesn’t indicate a problem; it only means that the vehicle hasn’t been driven in the right conditions to run the tests. The monitors will update to “readiness completed” as the vehicle is driven and the tests are performed. This may take hours, days, or weeks. Some vehicles are harder than others, and Fords are the most difficult of all. We’ve had some customers drive Mustangs for a month and still not get all the emissions monitors set. 

For many vehicles, the monitors will show “readiness completed” after a cold start, warmup cycle, and 20-150 miles of driving, but this is not guaranteed. You may never meet some driving conditions required to trigger the required tests.

A common issue we see is the situation when there’s no check engine light or diagnostic trouble code, but an emissions monitor stays “not ready” for days or weeks. Evap monitors on GM vehicles and catalyst monitors on Fords can be particularly problematic, potentially preventing you from passing emissions.

When a monitor status is “not ready,” it might not be from a tune reflash. It could be due to a recently disconnected or replaced battery, or the use of a diagnostic scan tool to erase trouble codes. That said, reflashing the engine control module (either to stock or a tune file) also resets all readiness monitors to “not ready.”

To reset the monitors to “readiness completed,” your vehicle may need to be driven in a specific way, known as a “drive cycle.” This sequence provides the conditions needed for the monitors to detect emissions issues. While the common advice to “drive it 50 miles” may randomly fulfill the drive cycle, it doesn’t always work.

If you’re having trouble getting all your emissions monitors to “readiness completed,” search online for the drive cycle specific to your vehicle’s make and model. Each vehicle manufacturer has different processes, some documented, some not.

Drive cycle steps can be unusual, such as “idle the engine for two and a half minutes with the air conditioner and rear defroster on” or “decelerate from 55 to 20 mph without touching the gas or brake.” These can be challenging, so ensure you have a long, clear road and be ready for curious looks or honks.

As a last resort here in Georgia, you can get an emissions waiver if you spend over $1,111 on emissions-related repairs. This is the 2024 limit, but it may change in 2025. Last year’s repairs don’t count towards the following year. The waiver is only good for one tag renewal. This means you will need to spend the required amount each year to get another waiver, and the state does increase the spending limit periodically.