Smog Tips

Smog City of Stockton advises the following to successfully complete your California smog test

Take your vehicle to a TEST-ONLY station – Smog City is a licensed Test Only station.

Test Only stations are not allowed to perform repairs or even recommend mechanics. This means that you will receive a truly unbiased test. While most shops are honest, Test & Repair stations have an incentive to fail your vehicle and perform the repair. The State of California established Test Only stations to assure consumers that they are being treated fairly.

Moreover, as a Test Only station, the only service we perform is smog checks. The trained and focused technicians at Smog City of Stockton will accurately examine your vehicle and have you back on the road as quickly as possible.

Choose a station that offers a FREE RE-TEST

Should your vehicle not pass its emissions test, Smog City of Stockton will perform another smog test for free. You may feel that your vehicle is running fine, but there are many elements that effect your vehicle’s emissions that may not be apparent to you. Why risk being double-charged? Choose a station, like Smog City of Stockton, that offers a FREE RE-TEST.

Our free re-test is available after you have repaired your vehicle and is valid for 30 days following the original test. Please note that an $8.25 smog certification fee is charged by the State of California upon passing your smog emissions exam. While we are required to collect this fee, it is passed on 100{59b89b038af6a6579077f1f5fdd668e9ca7d8c1f4e87521545b281945b1334db} to the State. Naturally, it is not charged on a failed test, but would be collected upon successfully passing your free re-test.


WARM your vehicle’s ENGINE:

Be sure that your vehicle is operating at normal temperatures before bringing it to Smog City of Stockton. A vehicle with a warm engine is more likely to pass a smog check. When your engine is warm, it burns fuel more efficiently. The catalytic converter will better oxidize pollutants coming out of the combustion chamber, meaning less harmful emissions and better smog test results. Especially on colder days, drive your vehicle for at least 20 minutes before we perform your smog test.


CHANGE your vehicle’s OIL:

If your vehicle is overdue for an oil change, have this service performed before bringing it to Smog City of Stockton. Vehicles needing an oil change may be burning fuel high in hydrocarbons and are therefore less likely to pass a smog test. An IMPORTANT note for 2000 and newer vehicles: Some oil changers will disconnect your battery during their inspection procedures. This will reset your vehicle’s memory chip used in the smog check process. A vehicle with an erased memory chip will not pass its smog test. Should this occur, just wait a few days before bringing your vehicle to Smog City of Stockton.



Nothing beats regular maintenance for ensuring that your vehicle will pass its smog test. A vehicle owner who follows the manufacturer’s schedule for regular maintenance is more likely to have a vehicle running at optimal fuel efficiency with fewer harmful emissions. Preventative maintenance will diagnose and correct issues before they become apparent during your vehicle’s smog check. If your engine is not idling smoothly have it repaired before getting a smog test.


DRIVE a good distance after connecting a BATTERY :

A new battery (or a disconnection of your old battery during maintenance) will clear the memory of the monitors on newer vehicles. With recently cleared monitors a vehicle cannot complete the smog inspection process. To reset your vehicle’s monitors, you will need to drive your vehicle a good distance. Unfortunately, there is not a standard amount of driving that will accomplish this. Generally, 30-150 driven miles and a few engine warm ups will do the trick. If you are unsure if your monitors are ready, bring your vehicle to Smog City of Stockton, where you can count on a FREE RE-TEST.


Repair your vehicle if the CHECK ENGINE LIGHT is on:

If your check engine or similar light is illuminated have your vehicle diagnosed and repaired before bringing it to Smog City of Stockton. A vehicle cannot pass a smog test if the check engine light is on, even if it successfully meets all emission requirements. The state puts smog technicians in a tough position over this requirement. Consumers are rightfully frustrated that technicians continue their smog test procedures even after seeing an illuminated check engine light. Every technician is rated by the state and these ratings are not only a source of pride but can be critical to their livelihood. Aborted tests negatively impact a technician’s report card with the state, therefore they will always complete all procedures even after becoming aware that a vehicle will not pass. This is another reason why Smog City of Stockton offers a free re-test. We do not want our customers or our technicians to be penalized by this issue. Of course, you will save our time and yours if you resolve check engine light issues before bringing your vehicle to Smog City of Stockton.


Maintain proper TIRE PRESSURE:

Proper tire pressure allows your vehicle to run smoothly and efficiently, not only on the road, but also when on our dynamometer during the smog inspection process. The manufacturer’s specifications for tire pressure for your vehicle will be found on a sticker on the driver’s side door jamb or in the glove compartment or in the trunk.


Fill your GAS TANK (older vehicles):

It requires a bit more time to test 1995 or older vehicles. These vehicles require an additional EVAP test, where the gas tank is filled with nitrogen to test if it holds pressure. A full tank will reduce the time required for this test and put you back on the road more quickly.