M278 P026A00 error - efficiency of the charge air cooler is not sufficient (2012 CLS)
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Joined: Jan 2020
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W222, W221, W218, W211
M278 P026A00 error - efficiency of the charge air cooler is not sufficient (2012 CLS)
Came across this today while fixing another thing on the car: P026A00 "the efficiency of the charge air cooler is not sufficient". The car is 2012 CLS 550 used in extreme weather conditions. The error is not permanent (last occurrence about 500kms ago), there CEL did not pop. But as temperatures outside climb up high, I am expecting it to come back. I did notice the car often acts like it doesn't want to accelerate as it used to, feeling sluggish, but again - it's hot outside.
Does CLS 550 even have a secondary air charge pump? Does it require any maintenance (e.g. separate coolant circuit that needs flushing maybe?). Curious to see troubleshooting options. I did replace the radiator couple of months back as the old one was leaking. I remember that the old one had distinctly different return inlet, while the new one had covered up - or highly restricted, as it turned out, since it's working fine and the car is not overheating by any means. I'm located in Dubai - so it's like a Death Valley here but for 11 months a year... I can get why the intercooler is struggling.
Any ideas?
Does CLS 550 even have a secondary air charge pump? Does it require any maintenance (e.g. separate coolant circuit that needs flushing maybe?). Curious to see troubleshooting options. I did replace the radiator couple of months back as the old one was leaking. I remember that the old one had distinctly different return inlet, while the new one had covered up - or highly restricted, as it turned out, since it's working fine and the car is not overheating by any means. I'm located in Dubai - so it's like a Death Valley here but for 11 months a year... I can get why the intercooler is struggling.
Any ideas?
Senior Member
Joined: Jun 2020
Posts: 417
Likes: 182
From: Finland
2015 CLS550 Shooting brake 4-matic
Hi. Maybe your IC water pump is broken or not working properly? My car is year model 2015 and my pump was leaking and I did change it same time when I upgrade my turbos.
