I'm struggling to get my OBD2 system ready for emmisons testing. I have been driving normally and still they're not all ready and I don't know what to do!

Auto shops have no idea what I'm talking about and it was my first time hearing about this when it happened to me. My manual has no information on it and there's no conclusive information online.

Using an obd2 meter i know I only have the evaporative system check left but there's no conclusive or official information on what I need to do to get it to pass

  • Welcome to Motor Vehicle Maintenance & Repair! Which part of the drive cycle isn't completing? Aug 29, 2023 at 23:37
  • Presuming you're describing all readiness monitors have completed and passed, leaving the evap system incomplete, is this the result of a recent repair or manually resetting an error code? Here's one site describing the evap system; aa1car.com/library/evap_system.htm. This can be a loose gas cap, corroded/leaking vent line (hard steel line or rubber hose), faulty/intermittent vent valve, fuel vapor pressure/vacuum sensor on the fuel tank. etc. ASE certified techs can diagnose a readiness monitor not completing and perform troubleshooting of the evap system plumbing and components.
    – F Dryer
    Aug 30, 2023 at 1:00

1 Answer 1


Your evap readiness monitor may not set if your fuel tank is more than 3/4 full.

You haven't stated your location, but in some jurisdictions such as California, you can pass if all monitors have run except evap, as long as the check engine light is not lit. This is because conditions have to be just right for the evap monitor to set, and it can take a long time or it may not set at all if, for example, you are at a high elevation.

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