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2002 Buick Century Question: Drive cycle

 

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kj1326, 3.1L V6, Southington, CT, August 27, 2011, 09:01
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i have taken my car 3 times to emissions and each time the test aborts. they tell me to drive the car more and more. I replaced the cat about 250 miles now and it still wont pass the test. does anyone know how many miles until the drive cycle resets for this car?

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  • Answer #1

    patrick mannion from Greg Solow's Engine Room, August 27, 2011, 10:07
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     Master

    Drive cycles vary from car to car and some are awful to get to pass. Have they told you which "monitors" have not yet passed?
    The following is a summary of generic OBD II drive cycle instructions 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.

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    kj1326, August 27, 2011, 17:27
     Rookie

    Yes they said it was the cat and odb2 that wasn't working everything else was reading.

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  • Answer #2

    mastertech6371 August 27, 2011, 18:38
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     Master

    to add to Pat. we never give them back to the customer for a drive cycle. you may drive it for 500 miles and never set 1. it is a very specific way of driving that makes the monitors run. take it somewhere else and have do the cycle for you. it will cost 1 hour in labor but well worth it.

    Roy

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