What does failing the emission test mean?
Your vehicle’s emission system is not working properly and is excessively polluting.
You must repair your vehicle until it passes (retest) or until all needs for a cost-based waiver are met.
Vehicle inspection station will give you:
You get one free re-inspection at the same station within 20 business days (except holidays and weekdays of date paid.) Repairs do not have to be at the same testing station.

Repairing Your Vehicle
Who can repair my vehicle?
Anyone can do needed repairs for the vehicle. You do not need to get repairs at the station that did your emission test. The choice of who does the emissions repair may affect waiver options.
Who can repair my vehicle?
Anyone can do needed repairs for the vehicle. You do not need to get repairs at the station that did your emission test. The choice of who does the emissions repair may affect waiver options.
Vehicle warranty
Repairs may be covered by a manufacturer’s warranty. Check your vehicle’s owner’s manual or contact a dealership for details.
Finding a repair technician
Anyone may repair your vehicle. However, labor costs can only be applied to a cost-based waiver if the work was done by a Missouri Recognized Repair Technician (MRRT). You can check websites like the Missouri Attorney General’s Know MO and the Better Business Bureau before selecting a repair station.
Bring paperwork
After the emissions test you got a vehicle inspection report. Give this to the repair technician and make sure the repair data sheet is properly filled out by whoever does the repairs. You must have this information for a retest.
Pre-repair inspection
You must have a pre-repair inspection before any emissions repairs are made in order to get a cost based waiver. This inspection should expand on error codes in the vehicle inspection report. Using diagnostic tools, a skilled automotive technician should use manufacturer diagnostic procedures to repair the causes of failure. The vehicle inspection report (issued when getting failing information) should be given to whoever repairs the vehicle to make sure they fix the correct problems.
Necessary repairs
In order to have emissions related costs applied to a cost based waiver, repairs must be qualified as necessary to correct the emissions related failures. The best way to qualify repairs is to show that the Diagnostic Trouble Code (DTC) from the first inspection is removed and a write-up diagnostic analysis.
Written diagnostic analysis should include:
Should a motorist repair the vehicle or direct a shop to repair, the burden of qualification is on the motorist.
A “Not Complete” emissions monitor does not mean a repair or replacement is needed.

Retesting Your Vehicle
Re-test your vehicle after repairs (for free if at the original shop within 20 days of first failing emissions test.) You should drive your vehicle for four to seven days in city and highway conditions before testing to get readiness monitors ‘Completed/Ready’.
Twenty Day Time Limit
To get one free retest at the same station you must have repairs within twenty business days of the first emissions test. After 20 business days you will have to pay for the full emissions test again.
What to bring to retest
Failing the retest
Fail for “Readiness Result”
Fail for same DTC that was repaired
Fail for a new DTC
For more information see Frequently Asked Questions About Emissions Waivers.