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Thread: Emission Testing/Ways to Cheat?

  1. #1
    Senior Member
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    Apr 2008

    Default Emission Testing/Ways to Cheat?

    I just received my emissions notice here in Illinois and it only uses a readiness monitor check without the tailpipe sniffer. My question is: What if i was to turn off a few codes so they are not reported to allow the light to be off and the monitors to be alive. The reason im saying this is becasue i have a light on due to Crank relearn not performed and is being a B***H to resolve. Im still working on idle transitions and smoothing out the quick movements of the throttle. So if I was to just not report the code for emissions, i can reflash the pcm, drive it til the others monitors are up, and take it in for a test?

  2. #2
    R.I.P Shawn, 1956-2011 WeathermanShawn's Avatar
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    Jul 2008


    I am not going to tell you how to break the law, but having lived in IL at one time I along with many others faced similar problems.

    First, I would always encourage you to fix your crank relearn code for your own sanity. I will only tell you that there is a right way and a wrong way to work the emissions reporting codes.

    I would work with someone locally to work your tune. If you just turn off the MIL code, IL may catch it.
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  3. #3
    Lifetime Member mr.prick's Avatar
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    Nov 2006


    Don't mess wit the Engine DTC Processing Enablers!
    reset your codes, and to pass the readiness test do this:

    Performing a GM OBD-II Driving Cycle:

    Cold Start.
    1. In order to be classified as a cold start the engine coolant temperature must be below 122°F (50°C) and within 11°F (6°C) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.

    2. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.

    3. Turn off the air conditioner and all the other loads and apply half throttle until 55mph (88km/hr) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.

    Hold Steady Speed.
    4. Hold a steady speed of 55mph (88km/hr) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.

    5. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 20 mph (32km/hr). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.

    6. Accelerate at 3/4 throttle until 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 3.

    Hold Steady Speed.
    7. Hold a steady speed of 55mph (88km/hr) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.

    8. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.
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  4. #4
    Senior Member
    Join Date
    Apr 2008


    Thats what i was wondering about WeathermanShawn. The Enablers is what i was wondering about. Since i am running a 383 in an 01 s10 with no emissions or convertors, there is no way i could drive the OBD drive cycle to get the monitors up. I have a lot of emission components removed to provide the engine with the most power and torque.

    Thanks weathermanShawn for the directions, this should help me not report a few codes so the system will be in ready mode. I am running short on time with school and work to give me ample time to work on this tune, but i am swapping out to long tube headers and changing the rear gears to 4.11s so i would like to get it past the emissions since it is due this month. I doubt i would able to re-tune the truck after changing the headers and geras before the month is up.

  5. #5
    Lifetime Member Chevy366's Avatar
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    Oct 2006


    Yeah , have had trouble with the SRT also , lucky Texas lets you have one failed SRT [system readiness test], and mine was the EVAP canister .
    Seems the EVAP takes a lot to reset and the routine described will not successfully set the EVAP as ready .

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