GLS Class (X166) Produced from 2016 to 2019

P1523 Check Engine light 2019 GLS450

Old Oct 28, 2024 | 08:55 AM
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2019 GLS 450
P1523 Check Engine light 2019 GLS450

Hi all,
Has anyone experienced this P1523 code for the check engine light? Car seems to drive normally but what did you guys do to fix this?

This same P1523 code/check engine light came on about 2 months ago but it went away on its own after adding a little bit oil and redoing the gas cap. I don’t know if it’s a coincidence or sensor issue or another intermittent issue that is not resolved? Do you guys know what code comes up when it’s due to the gas cap?

Thank you!
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Old Oct 28, 2024 | 09:04 AM
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Check cam magnet connectors and cam sensor connectors for signs of oil.
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Old Oct 28, 2024 | 09:19 AM
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Originally Posted by chassis
Check cam magnet connectors and cam sensor connectors for signs of oil.
Thank you. I forgot to mention that message for that code said “The check valve of the evaporator emission control system (at partial load) is jammed open.“

Last edited by Pmdonca; Oct 28, 2024 at 12:14 PM.
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Old Oct 28, 2024 | 09:38 PM
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Originally Posted by Pmdonca
Thank you. I forgot to mention that message for that code said “The check valve of the evaporator emission control system (at partial load) is jammed open.“
Looks like others have had their purge lines replaced.
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Old Oct 28, 2024 | 10:11 PM
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Originally Posted by thtguy
Looks like others have had their purge lines replaced.
The check engine light went away on its own again about 1 day later, when I re-tightened the gas cap. Is it possible that’s the error code for loose gas cap?
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Old Oct 29, 2024 | 06:47 AM
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Originally Posted by Pmdonca
The check engine light went away on its own again about 1 day later, when I re-tightened the gas cap. Is it possible that’s the error code for loose gas cap?
P0456 (evap small leak detected) is usually gas cap. But if tightening gas cap fixed it, then maybe that was causing the issue.
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Old Oct 29, 2024 | 08:41 AM
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Five clicks...
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Old Oct 29, 2024 | 01:45 PM
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Originally Posted by thtguy
P0456 (evap small leak detected) is usually gas cap. But if tightening gas cap fixed it, then maybe that was causing the issue.
Thank you! I am thinking the code that I got is also another code due to the gas cap bc it went away after retightening cap to 3-6 clicks. Same code and same thing happened last time about 2 months ago. I did not add nor did I need to add oil this time. Likely a gas cap issue unless it’s another intermittent issue… I educated my wife on going past at least 3 clicks so hopefully this won’t happen again. If it does happen, then it will make me think it’s an intermittent issue… Please share any other ideas I may be overlooking, it will
be greatly appreciated!
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Old Oct 29, 2024 | 01:57 PM
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2 things it has taken a bit to get used to, the non positive closing gas cap, like on every Mercedes Car I have owned. And the non floor mounted accelerator pedal. It is weird the little things you notice.


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Old Oct 29, 2024 | 02:11 PM
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Originally Posted by thtguy
2 things it has taken a bit to get used to, the non positive closing gas cap, like on every Mercedes Car I have owned. And the non floor mounted accelerator pedal. It is weird the little things you notice.


Thank you. We had 2006 ML500 before this one. We did not have any issues with the gas cap. We just gotta make sure to go past 3 clicks with this one and see if the check engine light comes up again.
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