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Q: 01 buick century will not set evap or catalyst no matter what i do on 2001 Buick Century

done drive cycle 1oo times no codes and no mil light ;-)
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Evap test is hard to get to pass but it is critical to make fuel level in the tank is correct. I attach a generic "drive cycle" chart that must run to pass all the monitors. Not sure about NY but some states allow one monitor to not yet have passed.
The Intake Air Temperature (IAT) should be between 14 and 122 degrees F. Barometric pressure should be equal to or greater than 75 kPa. The fuel tank should be between 25 and 75% full at the start of the test. During acceleration, keep throttle 1⁄4 to 1⁄2 open. During deceleration, slow to less than 15 mph at an engine speed of less than 1000 rpm without touching the brake or clutch pedal. During cruise, maintain a steady engine speed between 1400 and 4000 rpm. At idle speed, keep the throttle closed and the gear selector in the Neutral position. Remember, these are just the preliminary instructions. The actual drive cycle must conform exactly to the following instructions, or the various monitors may not run to completion. The drive cycle begins with a cold engine startup. The IAT must be between 32 and 85 degrees F. Engine Coolant Temperature (ECT), must be less than 127 degrees F. It may be necessary for the customer to leave the car with you overnight so it can cool down completely. The engine coolant and intake air temperatures must be within a tight range to complete all of the OBD II monitors during the drive cycle. If the IAT input is not between 32 and 86 degrees F at the beginning of the drive cycle, the EVAP monitor will not run. Start the engine and allow it to idle in Park for one to two minutes. Within the first minute and a half, accelerate at 1⁄4 to 3⁄4 throttle to 50-55 mph. Hold that speed for 2-3 minutes. Unless your shop is very close to a major expressway, it may be difficult to satisfy this step in the drive cycle. Decelerate to 0 mph without braking, then idle for 1-2 minutes. If you’re on an expressway, pull safely off the road during this segment. Accelerate to 55 mph, using 1⁄4 to 3⁄4 throttle, then hold a steady cruise for 10 to 20 minutes. Return to 0 mph with the engine idling in Park, then turn the ignition off.
Thank you for your help I will try this drive cycle too and see what hapens My shop is about 1 mile from the nys threw way so I do most of my drive cycles on there and mostly late at night when trafic is not so heavy So I am prity much doing it to a t but still no luck with this car It does have a stubern streak I will let you know more later Thanks again Jim
This will need a mode 6 diagnosis. It takes a really good technician to understand 'mode 6' diagnosis of failing monitors. First thing to check is make sure that your battery and charging system are in excellent shape, then study the performance of the oxygen sensors, because the catalyst monitors key on that. If it is too cold or too hot, the EVAP monitor will not even run, so be aware of that, since it is
Thanks for the reply I have done the drivecycle sevral times to what my snap on modis said to do and also the generic drive cycle batery and alternater are strong the odometer on this car is digital and I can not see the milage but I must have put at least 500 miles on it and no check engine light or codes but it will not run the evap or cat I had a code po446,po128,po1189and p1811 we droped fuel tank and repaird gas gage and installed new evap charcoal canesterand new vent solenoid cleared memory and I can not get these two moneters to set since then I have wavered the inspction for now as we have way too much time and money I will see waht happens in a few thousand miles Let me know what else you think thank you Jim
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