2005 silverado evap monitor not ready
12-15-2019, 07:23 PM
#1
TECH Fanatic
Thread Starter
2005 silverado evap monitor not ready
No check engine light on.. no symptoms... im stumped... what causes this? I already drove it 300 miles since last repair ... or how long does it tale for a driving cycle to complete
12-15-2019, 11:57 PM
#2
It has to meet a certain criteria to run the monitor.
This is the basic recomended drive cycle General Motors Driving Cycle
https://rangetechnology.zendesk.com/...itor-procedure
This is the basic recomended drive cycle General Motors Driving Cycle
https://rangetechnology.zendesk.com/...itor-procedure
12-17-2019, 10:35 AM
#7
You can usually have 1 not ready
EVAP is the hardest one to get to go through. I have had a tough time with them but usually I have the best luck if the vehicle is between 1/4 tank and 3/4 tank and do cold start long warm ups, which is let it set overnight to fully cool and then start it and let it run until fully warm, or about 10-15 minutes. Do that a few times and see if it helps.
Usually if a vehicle has a monitor that just wont go through, or several, it's because the PCM is detecting a malfunction and is either setting a pending code or about to set a hard code and trigger the check engine light. So for example if you are doing a drive cycle and trying to get all monitors to go through and you're sitting there watching them switch from not ready to ready and all the sudden they stop going ready and you can't get any more to go through, you'll usually find that if you go and check pending codes there will be a pending code. Once the PCM detects an error it fully stops the process of monitors going ready.
There are a few GM's out there I have ran into in my years that will actually never go through. But my customers with those either still passed due to being able to pass with one not ready, or wrote a letter to the state and got a pass on the not ready due to the circumstances. But I believe they make you meet certain criteria first, like spending x amount of dollars trying to fix the issue in that year, I think it's around $600 here in texas. I say that because since everyone has found a way to pass, we never did actually find out why the monitor wouldn't go through. And in the examples i'm using these folks had the monitor not go ready for like 2-3 years and was never going to. I assume the repair would involve either reprogramming the PCM or replacing it.
EVAP is the hardest one to get to go through. I have had a tough time with them but usually I have the best luck if the vehicle is between 1/4 tank and 3/4 tank and do cold start long warm ups, which is let it set overnight to fully cool and then start it and let it run until fully warm, or about 10-15 minutes. Do that a few times and see if it helps.
Usually if a vehicle has a monitor that just wont go through, or several, it's because the PCM is detecting a malfunction and is either setting a pending code or about to set a hard code and trigger the check engine light. So for example if you are doing a drive cycle and trying to get all monitors to go through and you're sitting there watching them switch from not ready to ready and all the sudden they stop going ready and you can't get any more to go through, you'll usually find that if you go and check pending codes there will be a pending code. Once the PCM detects an error it fully stops the process of monitors going ready.
There are a few GM's out there I have ran into in my years that will actually never go through. But my customers with those either still passed due to being able to pass with one not ready, or wrote a letter to the state and got a pass on the not ready due to the circumstances. But I believe they make you meet certain criteria first, like spending x amount of dollars trying to fix the issue in that year, I think it's around $600 here in texas. I say that because since everyone has found a way to pass, we never did actually find out why the monitor wouldn't go through. And in the examples i'm using these folks had the monitor not go ready for like 2-3 years and was never going to. I assume the repair would involve either reprogramming the PCM or replacing it.
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12-17-2019, 05:49 PM
#9
One thing that fails that I see most techs miss is the tank pressure sensor on the fuel pump. On GM cars it's somewhat common for them to get stuck and you'll get a vent valve malfunction code when they do. The pressure sensor is mounted on the pump, on the top hat, by the electrical connector for the pump and looks exactly like a MAP sensor. It has a small electrical connector going to it too.