EVAP not ready

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Reyetwinger

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Hi. I had a P0138 and P0158 code on my 2020 Tahoe with the 5.3. I took it to the dealer (one month out of warranty) and they cleared the codes and did a fuel system cleaning. They are telling me the gas sat too long and separated. This isn't true but that was their only explanation.
The EVAP system monitor is still not ready after trying to perform a few driving cycles. I have between 1/2 and 3/4 of fuel in the tank. Cold started and let the truck idle for 2.5-3 minutes with the AC and rear defroster on. Turned off AC and defroster, and when I got to a highway accelerated up to 55 MPH and set cruise and held steady speed for 3 minutes, disengaged cruise and decelerated to 18 mph. Accelerated again with more throttle to 57 mph, set cruise and held steady for 5 minutes and again decelerated to 18 mph. I did this 3 times and the EVAP is still not ready to monitor.
Does anyone know what specific part of this drive cycle gets the EVAP into a ready state, or does the whole cycle have to be performed? It would be much easier if I could concentrate on this one system and avoid all the rest of this crazy driving cycle. There are no codes, stored or pending, 0 DTC. Thanks.
 

Fless

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Is there a particular reason that the evap monitor needs to be set?
 
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Reyetwinger

Reyetwinger

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I would just like all the systems to be functioning. Being that I was throwing codes I would like to see all green lights at some point. Luckily right now I don't live in a state that requires all the monitors to be testing to pass inspection. I'm also wondering why I'm not getting a ready since I believe I'm following the drive cycles.
 

Fless

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Most states that test for emissions allow one monitor not to be set, for exactly this reason. I'd say that if you're not getting an evap code tripping the CEL, it's fine.
 
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