OBD and Emissions Testing

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In my state the emissions test for my '98 Civic is now an OBD test. My car has an intermittent misfire when it starts in damp weather and turns on the MIL light - however after several driving cycles the MIL light goes off and remains off. My question is - if the MIL light os off is there still freeze frame memory of the misfire problem in the memory? I ask since I want to pass the emissions test and want to make sure if I go for the test with the MIL light off that there won't be some stored codes in the memory that will cause me to fail the emissions test?

Should I take the fuse out to reset the memory before I go for the test?

posted by  alongtheroad

Hmmm. I'll have to think about that while you visit the "Introduce Yourself" section.

posted by  vwhobo

you need to fix the misfire to keep raw fuel from ruining your catalytic converter. Once you fix the problem and get no check engine light, you can clear the codes with a scan tool or a code reader. Removing the fuse will not clear an OBD2 computer.

Once the codes have been cleared, drive the car a few days before taking the car to the emissions test. The OBD2 ECM has a certain number of self tests it does and records they have been done. Clearing the OBD2 also clears the results of the various self testing routines which the emissions inspector is looking for when he/she hooks a scan tool to your cars data link. . The car has to be driven in certain sequence for 15-20 minutes (normal commuter driving will typically do this in a couple of days) for the system to perform all of its tests and set trouble codes if any. A car from 1996 to 2000 can have two of these computer system self tests not complete, the 2001 and later models can only have one of these computer system self tests not done. More tests incomplete than the above numbers is an automatic failure in most states with emissions inspections.

Also note a burned out check engine light or one that is on in KOER mode (key on engine running) will also result in emmissions failure

posted by  tbaxleyjr

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