Unknown fault code after AEM install
Thread Starter
Junior Member
Joined: Oct 2018
Posts: 22
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GLK250
Unknown fault code after AEM install
Hey all,
Has anyone had any issues after their AEM install? (14 GLK250)
I keep getting a CEL light come on and go out randomly after the AEM install. I took it to my local Mercedes shop and they told me it's coming up on their computer as an unknown fault. The diagnostics were done on a Mercedes specific computer and the technician said it's likely a software issue related to the AEM install.
The light will be off for a week or so then come on for an hour, a day, or more then go out. Completely random, and no noticeable difference in the driving.
The dealership wants $220 for the diagnostic, taking 2 days, with no loaner - so i'm trying to understand this before sacrificing myself to this evil.
Has anyone had any issues after their AEM install? (14 GLK250)
I keep getting a CEL light come on and go out randomly after the AEM install. I took it to my local Mercedes shop and they told me it's coming up on their computer as an unknown fault. The diagnostics were done on a Mercedes specific computer and the technician said it's likely a software issue related to the AEM install.
The light will be off for a week or so then come on for an hour, a day, or more then go out. Completely random, and no noticeable difference in the driving.
The dealership wants $220 for the diagnostic, taking 2 days, with no loaner - so i'm trying to understand this before sacrificing myself to this evil.
MBWorld Fanatic!
Joined: Jul 2012
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From: WI
GLK 250
Any chance you're on the original battery still? Weak batteries have been known to produce weird electrical gremlins. You could stop by your neighborhood AutoZone and have them scan the car, they'll give you the trouble code(s) printout.
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GLK250
Hopefully I get them by the end of Wednesday. If it is software related, where does that leave me? Can they possibly want money if I somehow have the incorrect/bad software?
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MBWorld Fanatic!
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From: WI
GLK 250
No. If it's ECU related, that's covered under the AEM. In fact, a ton of stuff is covered under the AEM; we just need to start with some codes so we have an idea of what it might be.
I'm thinking something related to the emissions system, maybe the AdBlue system or EGR valve. Without codes, we're just guessing.
I'm thinking something related to the emissions system, maybe the AdBlue system or EGR valve. Without codes, we're just guessing.
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From: Ontario
2012 GLK350 4MATIC
I don't know if this will help, but my 2012 glk 350 CEL would randomly come on as well. It always seemed to happen on the colder & damper days of the year, my mechanic told me it was one of the 2 check valves for the A.I.R. system. He cleaned it free of charge & it solved my issue for a few weeks, then the CEL came back & the secondary air pump started squealing at cold start. The Secondary air pump only turns on for about 10 secs when you first start the engine.
After I did some research and ordering parts I had my mechanic change the secondary air pump, both check valves and the change over valve. I think this has solved my issue for now. Here is a link to a helpful diagram of the A.I.R. system:
A.I.R. SYSTEM for 2012 Mercedes-Benz GLK 350 | Mercedes-Benz USA Parts (mbusa.com)
After I did some research and ordering parts I had my mechanic change the secondary air pump, both check valves and the change over valve. I think this has solved my issue for now. Here is a link to a helpful diagram of the A.I.R. system:
A.I.R. SYSTEM for 2012 Mercedes-Benz GLK 350 | Mercedes-Benz USA Parts (mbusa.com)
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GLK250
So I just got word back from the dealership, the fault code is P208027 (Temperature sensor 1 "Exhaust System" cylinder bank 1 has a malfunction, the signal change rate is above permissible value.)
They aren't certain, but believe it's this turbo temperature sensor that needs replacing $990
I'm getting the part number to see if it is one that's listed for the extended AEM warranty, but offhand does anyone have experience with this?
Edit: Part number they are giving me is 000-905-93-05 which replaces part 000-905-83-05
Mercedes website has this when searching for either number
They aren't certain, but believe it's this turbo temperature sensor that needs replacing $990
I'm getting the part number to see if it is one that's listed for the extended AEM warranty, but offhand does anyone have experience with this?
Edit: Part number they are giving me is 000-905-93-05 which replaces part 000-905-83-05
Mercedes website has this when searching for either number
- Genuine: Mercedes
- SKU:000-905-93-05
- Other Names:Temperature Sensor
- Description:E250. Gle300d. To 1/8/16. Exhaust gas temperature. Upstream of turbocharger. Frt. of charge air cooler.
- Condition:New
- Replaces:000-905-83-05
- Sold In Quantity:1
Last edited by mgrych; Oct 28, 2021 at 04:59 PM. Reason: new info
MBWorld Fanatic!
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From: WI
GLK 250
Keep on them to take care of it free of charge. The turbos (there's a low side and a high side) are covered under the AEM campaign, so anything on the turbo or that enables the turbo to work is therefore covered, whether that's a sensor, the wastegate actuator, whatever.
Press them and call MB corporate as well, right from the service advisor's desk if you have to.
Do not, i repeat, DO NOT pay out of pocket.
Here link is the list of covered components, on pages 3-4. Print it out if you have to and bring it with you.
Press them and call MB corporate as well, right from the service advisor's desk if you have to.
Do not, i repeat, DO NOT pay out of pocket.
Here link is the list of covered components, on pages 3-4. Print it out if you have to and bring it with you.
Last edited by andreigbs; Oct 29, 2021 at 09:53 AM.
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GLK250
Update: They rejected my appeal to have the sensor replaced, using my list of parts under the extended warranty (same list you attached). I called corporate and spoke with an agent but they knew very little regarding this, so they escalated my case to some type of special investigative supervisor..? He actually returned my call, collected some info, and did some digging himself. By the end of the day, he had contacted the dealership and spoke with the service manager and warranty person (not the service advisor though).
They've concluded that the temperature sensor is in fact.. get this... a temperature sensor - much like the one listed in the paperwork. So it is covered and will be replaced in a week or so.
As this is the second time I've had to do this (DEF pump and temperature sensor) I've concluded that if you want the dealership to warranty repair anything on that list of parts covered; you have to contact corporate and go through this entire process.
They've concluded that the temperature sensor is in fact.. get this... a temperature sensor - much like the one listed in the paperwork. So it is covered and will be replaced in a week or so.
As this is the second time I've had to do this (DEF pump and temperature sensor) I've concluded that if you want the dealership to warranty repair anything on that list of parts covered; you have to contact corporate and go through this entire process.
