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OBD and Emissions Testing

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  • OBD and Emissions Testing

    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 is 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?

  • #2
    If u pull the fuse right before the test, the Readiness Monitors won't be set and you will fail the inspection. You have to drive a while for them to be set.


    • #3
      As far as I know from my line of work (Fords) the code will still be etched in memory until it is reset, and at that point it becomes a P1000 until it clears all the necessary drive cycles. Even thought the light may be currently off, it still knows that there was a problem. A car with a P1000 pass code will not pass thru emmissions, so you cant just clear the code and drive thru. It must pass all tests before the P1000 goes away.
      2005 Ford Focus ST


      • #4
        Can someone explain all this jargon? Don't have emissions testing in Pennsylvania.


        • #5
          Actually, Penn is currently rolling out OBD2 emissions testing as we speak. How that impacts you is dependent on what county you live in. Pittsburgh area is now rolled out. Philli is coming very soon. Philli also requires a gas cap pressure test with the emissions test.

          The state mandated the tool companies to design tools that looked for certain conditions. If you pull the fuse and "clear the error code", then the vehicle has to run a while before the controller turns off the Readiness Monitor. This is to prevent someone from pulling fuse on the wait for the inspection and be approved with a poorly running (out of spec) vehicle.

          The idea behind OBD2 inspections is that the Govt forced the vehicle manufacturers to implement complicated systems to make sure the vehicle was running clean, and monitoring systems to tell the driver if it wasn't. Historically, the emissions test (for states that implemented testing) was an exhaust gas sniff test at idle. This was expensive equipment that needed maintenance. Then some states legislated dynamometer sniff testing (more very expensive equipment to buy). In the end they said - hmmmm, the car has an even more sophisticated system to monitor during all driving conditions...let's just see if the car is tampered with, and if not, pass emissions if the OBD system says it is running fine.

          So, your car is a rolling emissions test station. The majority of states have legislated this change. North Carolina and Penn are two of the first to implement. Many more to follow soon.