P0128 Thermostat Error
Thread Starter
Junior Member
Joined: Nov 2014
Posts: 57
Likes: 3
From: Savannah, GA/Mystic/CT
2009 E350 4matic wagon, 1980 450SL, 2011 GL450
P0128 Thermostat Error
I got a check engine light on my 2009 E350 wagon. Car was driving fine so I read the code-P0128 thermostat not closing- I reset and have driven over 200 miles with no CEL and no issues. Temperature gauge reads 80-90 degrees C before, during , & after CEL came on. Temperature appears to be very steady.
Any insight or just an anomaly as the car had sat about 4 weeks prior to this episode.
Any insight or just an anomaly as the car had sat about 4 weeks prior to this episode.
Thread Starter
Junior Member
Joined: Nov 2014
Posts: 57
Likes: 3
From: Savannah, GA/Mystic/CT
2009 E350 4matic wagon, 1980 450SL, 2011 GL450
I don't think so. 2-3 minutes before gauge begins to read 40-45 degrees (50 degrees F ambient) Full temp within 3-5 minutes & 3-4 miles.
MBWorld Fanatic!
Joined: Jan 2016
Posts: 2,758
Likes: 889
From: In the Shadow of the Tetons
2013 ML350 Bluetec
I'd just drive it, while observing warm up times. I let my car sit for the month of November while I was out of country. The glitch I noticed was the windshield washer fluid did NOT work for a couple of ignition cycles. Push the stalk halfway, the wipers wipe like you'd expect. Push the stalk all the way to the fluid dispenser position, it was just like pushing halfway: The wipers would stop after completing one cycle after releasing, and no fluid would come out. The problem went away as quickly as it appeared and hasn't been seen since early December.
Anecdotal evidence, for sure, but... Just drive it. If it happens again, take action.
Anecdotal evidence, for sure, but... Just drive it. If it happens again, take action.
Super Member
Joined: May 2011
Posts: 978
Likes: 274
From: Fort Worth TX
2020 S560, 2014 SLK55 (Prev. 2016 S65, 2013 SLK350, 2008 CLS63, 2006 E350, 2006 CLS500, 2005 C230K)
Thermostat is likely sticking, recommend removal for inspection and coolant replacement.
This is an electric assisted thermostat so it is a bit pricey if it fails.
This is an electric assisted thermostat so it is a bit pricey if it fails.
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,550
From: MA
2008 E350 4Matic, 2011 E350 4matic
It's very common for them to go. I replaced the one in my 2008 several years ago. OEM is a Wahler. I think I got mine on Amazon for around $70. It actually has the spot where the MB logo would be blurred out. It was pretty noticeable on a cold day, car never really warmed up beyond 80. Now it's usually at least 90+. You might also want to check your pulleys and tensioners, those are also common failure items on the M272. I replaced mine at the same time as you have to remove one of the pulleys anyway in order to change the thermostat. I think the kit is around $122 on rockauto.com. There's also a discount code on retailmenot.com that takes off 5% so that kinda pays for the shipping.
https://www.rockauto.com/en/moreinfo...=1443226&jsn=2
https://www.rockauto.com/en/moreinfo...=1443226&jsn=2
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