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:

  • Vehicle inspection report that shows what part failed;
  • Repair facility performance report that lists the ten nearest Missouri Recognized Repair Stations; and,
  • Repair data sheet for the repair facility performance report.

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.

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:

  • Diagnostic work done by a skilled automotive technician.
  • List of proper diagnostic tools used and manufacturer determined diagnostic procedures specific to cause of failure.

Should a motorist repair the vehicle or direct a shop to repair, the burden of qualification is on the motorist.

A "Not Completed" emissions monitor does not mean a repair or replacement is needed.

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

  1. Failing vehicle inspection report.
  2. Completed repair data sheet (filled out by repair technician).

Failing the retest

Your vehicle will need to be retested until it receives a "Pass" or you have spent enough money to qualify for a cost-based waiver.

Fail for "Readiness Result" Drive 4-7 days and return to inspection station
Fail for same DTC that was repaired This means the repairs did not fix the problem. Show the repair station the failing vehicle inspection report and ask about any repair guarantees or warranty the shop may have
Fail for a new DTC The first repair may have let the vehicle's computer find more problems. Ask the repair person who worked on your vehicle to check their work and make sure nothing was missed.


For more information see Frequently Asked Questions About Emissions Waivers.