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so my truck failed inspection today due to the obd monitor readiness test the computer runs. the two systems that were "not ready" were 1) Evaporative System and 2) Oxygen Sensor Heater. the shop said that since i had just put a new battery in yesterday that the computer was reset and hadnt had time to properly re-calibrate itself. but he couldnt tell me how many miles im supposed to drive the truck to get it back in check, just "oh 80-100 miles you should be good." anyone got a definite mileage????
 

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thanks. im already over 125 miles, so i should be good by late next week.
 

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its not based on mileage, its based on conditions. So you cant get a real answer for how far you should drive. but 100 miles is usually sufficient. Some cars are harder to get set than others. The evap should set itself from just idling really, and the o2 sensor needs to get hot.
 

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The evap should set itself from just idling really, and the o2 sensor needs to get hot.
at the time it failed the test, i had driven the truck 3 times at more than 25 minutes each time and put about 50 miles on it. i may just say screw it, the inspection is still good till november from the previous owner so its not a big deal, really.
 

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6shooter - I know this is a really old thread but I am hoping you can shed some light on what you did to resolve this...Did your O2 sensor heater ever set to ready?? I am having the exact same issue. I bought a used truck that needs Smog inspection now. I'm just about up with my 30 day temp plates. I can't get O2 sensor heater and Evap to set to ready. I even replaced all 4 O2 Sensors! No check engine lights or codes. In Arizona I beleive I can smog it with 1 monitor not ready so even if I can get one of these to get one of these to set I will be good. Follow the GM Drive cycle many times. Spent much time letting it idle with A/C and rear defrost on. I understand Evap can be a pain to set but what is the deal with O2 sensor heater?? This should be one of the first to set. Any advice is much appreciated.
 

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Just get out and drive it on the highway a bit, then drive it around town a bit. Then drive it to autozone and borrow their scanner, it will tell you whether the system is ready for the test. The PCM only sets not ready if the battery is disconnected or any codes are cleared via scan tool.
 

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Just get out and drive it on the highway a bit, then drive it around town a bit. Then drive it to autozone and borrow their scanner, it will tell you whether the system is ready for the test. The PCM only sets not ready if the battery is disconnected or any codes are cleared via scan tool.
Been there done that. The truck was worked on before I bought it and codes were cleared at that time. Put over 500 miles on it over a month and couldnt get the O2 Sensor heater to set. Changed out all my sensors last week and still nothing. I have a tool so I can monitor myself. From what I understand the Sensor Heater is supposed to run with a cold start and letting the truck idle for a few minutes. Should be one of the easiest to get to set. I'm baffled. I'm in Arizona in the dead of summer - maybe its effecting the ability to do the required "Cold Start"
 

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I just drove it around for a few more weeks and took it back in, it passed. stupid emissions
 

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I just drove it around for a few more weeks and took it back in, it passed. stupid emissions
Thanks. yeah what a circus.. Lets have everyone drive around burning gas aimlessly for 500 miles to get the tests to run and prove there is no emissions issue. Glad to see my tax dollars are going to good use supporting these programs... Do you know if they both set to ready? Or were you allowed to have it tested with one not set?
 

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Thanks. yeah what a circus.. Lets have everyone drive around burning gas aimlessly for 500 miles to get the tests to run and prove there is no emissions issue. Glad to see my tax dollars are going to good use supporting these programs... Do you know if they both set to ready? Or were you allowed to have it tested with one not set?
if I remember correctly, I plugged my obd II scanner in and ran the ready tests, and like 3 read not ready. I said fuck it, and took it in anyway because it was due and I got a sticker.
 

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Been there done that. The truck was worked on before I bought it and codes were cleared at that time. Put over 500 miles on it over a month and couldnt get the O2 Sensor heater to set. Changed out all my sensors last week and still nothing. I have a tool so I can monitor myself. From what I understand the Sensor Heater is supposed to run with a cold start and letting the truck idle for a few minutes. Should be one of the easiest to get to set. I'm baffled. I'm in Arizona in the dead of summer - maybe its effecting the ability to do the required "Cold Start"
The ambient temperature really doesn't matter regarding "cold start" and O2 sensor readiness. The O2 sensors will always run the heat circuit at startup because they aren't up to optimum operating conditions until they reach 600* F. Waiting for the exhaust gasses to heat them up takes too long and they allow the engine to emit too much pollution until they are ready. Also, during extended idle times they will cool below 600* - so the heaters kick on again to bring them up to the proper temperature. This is why they are internally heated.
 
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