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Intermittent Check Engine Light 2019 GLS450

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Old Mar 17, 2025 | 04:06 AM
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2019 GLS 450
Intermittent Check Engine Light 2019 GLS450
Hi, I posted awhile back but the check engine light keeps coming up when the gas level is about half tank full or below and then goes away after refilling the gas. I thought it was from the gas cap not being tightened enough, but we crank it tight past 3 clicks after filling up the gas. As the gas level drops to below 1/2 tank is usually when the check engine light reappears until we refill the gas tank. Any idea what needs to be fixed? The car drives normal even when check engine light is on. We are just annoyed by the constant intermittent check engine light. Has anyone have heard of this type of situation and what it could be? Thanks.
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Old Mar 17, 2025 | 09:40 AM
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'17 GLS450, '14 GLK250, Grandpa's Roadster
When the check engine light comes on it means there is a fault code present. Have the code read and it will direct you to the fault.
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Old Mar 17, 2025 | 09:54 AM
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Replace the fuel fill cap with an OEM part purchased at the dealer. Report back.
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Old Mar 17, 2025 | 01:22 PM
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Two great suggestions above, I will add one, have your SA remotely scan for codes in the vehicle, and report back.
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Old Mar 17, 2025 | 01:23 PM
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https://developer.mercedes-benz.com/...nostic_support
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Old Mar 18, 2025 | 12:57 PM
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Did the SA get back on you what code is stored?
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Old Mar 18, 2025 | 03:48 PM
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2019 GLS 450
Originally Posted by W205C43PFL
Did the SA get back on you what code is stored?
P1523 is the code that always comes up for the check engine light. I ordered OEM gas cap and we will see if that fixes it permanently since this issue occurs intermittently. Any other suggestions/ideas if the new gas cap does not solve the issue? Thank you.
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Old Mar 18, 2025 | 09:36 PM
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Did they tell you what the code meant? I looked it up and got about 4 unrelated definitions.
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Old Mar 18, 2025 | 10:02 PM
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2019 GLS 450
Originally Posted by John CC
Did they tell you what the code meant? I looked it up and got about 4 unrelated definitions.
It was like a non specific code. It seems like the code didn’t really help at all.
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Old Mar 18, 2025 | 11:15 PM
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Originally Posted by Pmdonca
P1523 is the code that always comes up for the check engine light. I ordered OEM gas cap and we will see if that fixes it permanently since this issue occurs intermittently. Any other suggestions/ideas if the new gas cap does not solve the issue? Thank you.
Very generic code, honestly other than the gas cap I too don't have other suggestions.
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Old Mar 18, 2025 | 11:29 PM
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Perhaps there is a outstanding PTCU update or some other update that might address it?
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Old Apr 3, 2025 | 09:09 PM
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2019 GLS 450
Update
After getting a new OEM gas cap. The intermittent check engine light is still occurring. Any other suggestions or ideas? It is still the generic code as mentioned on an earlier post.
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Old Apr 3, 2025 | 09:17 PM
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Originally Posted by Pmdonca
After getting a new OEM gas cap. The intermittent check engine light is still occurring. Any other suggestions or ideas? It is still the generic code as mentioned on an earlier post.
What are some parameters you are aware of when it causes it, is the coolant good, what engine oil temperature?
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Old Apr 3, 2025 | 11:49 PM
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2019 GLS 450
No parameters that I notice, it is really strange. It seems like the check engine light usually occurs when the gas tank is between 1/4 to 1/2 tank.
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Old Apr 4, 2025 | 07:37 AM
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Originally Posted by Pmdonca
No parameters that I notice, it is really strange. It seems like the check engine light usually occurs when the gas tank is between 1/4 to 1/2 tank.
Sounds like the fuel pump.
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Old Apr 4, 2025 | 07:38 AM
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You might be affected by a fuel pump recall, there was a known bad supplier/supplied unit with a few MB models during certain model years, I am not sure if it applies to the GLS but worth a look.
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Old Apr 4, 2025 | 07:39 AM
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https://mbworld.org/forums/gle-class...mp-recall.html
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Old Apr 4, 2025 | 07:40 AM
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never mind, it only applies to 2021 to 2023, not the 2019 I would still look into the fuel pump though.
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Old Apr 5, 2025 | 08:44 AM
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Originally Posted by Pmdonca
After getting a new OEM gas cap. The intermittent check engine light is still occurring. Any other suggestions or ideas? It is still the generic code as mentioned on an earlier post.
Replace the purge valve. Should be clearly visible and accessible on the left side of the engine bay. If no joy consider replacing the carbon canister.

When were the main and aux batteries last reolaced?
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Old Jun 17, 2025 | 07:11 PM
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2019 GLS 450
Hi all, I wanted to provide an update. It ended up being the oil pump valve per diagnostic at Mercedes. It’s an expensive fix. Thankfully, I paid for the 1 year/12,000 mile warranty when purchased the car used. Thank you.
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