Had a little issue today with a spirited drive down to Denver. Was driving hard up and over Vail pass and got a drivetrain error - car said OK to continue and didn't need roadside. I had my Autel with me so pulled the codes while driving and had the following:
14401A - Super knocking, fuel disabled cylinder 4
152D08 - Super knocking all cylinders
20AU201 - Coolant Loss Detected
108B39 - Charge Air sensor 2 temp too high
I pulled over. Cleared the codes, asked chatgpt and then drove another 300 miles with no issues whatsoever including a return over Vail pass (although I didn't drive quite as enthusiastically on the way back).
Has anyone run into this before?
AI says I probably heat soaked it over the pass and combination of 91 fuel (highest we can buy in the mountains) and warm temps caused the error. Car seemed absolutely fine after clearing codes.
Any advice on what to check so it doesn't happy again? AI tells me to check the coolant level but apparently I have to wait until it's cool.
Car is mostly stock but has an Akrapovic exhaust. No tune, no downpipes.
Codes have not reappeared and apart from the drivetrain error, i didn't get a CEL or anything.
Perhaps someone has experienced something similar?
Lastly, I had filled up at City Market, is their fuel bad? I've since filled it with V Power which is what I normally use...
03-03-2026
I just did a quick google search on your second code, and it came up with this page in another section of Bimmerpost. https://f30.bimmerpost.com/forums/showthread.php?t=1722102
Reading through that, it may be an indication of a coil on the way out.
03-03-2026
I just did a quick google search on your second code, and it came up with this page in another section of Bimmerpost. https://f30.bimmerpost.com/forums/showthread.php?t=1722102
Reading through that, it may be an indication of a coil on the way out.
Ah I see - good catch thanks. I suppose I'll do coils and plugs as they haven't been done in 25k miles. Want to get the car running perfectly before tuning it!
05-09-2026
Just wanted to update this in case anyone else experiences the issue as it had rather an easy fix. The problem was the coolant was leaking from the secondary tank - and it was leaking through the cap. I replaced the cap a week ago and since then i've had no errors and haven't lost any coolant. The tell-tale sign was crusty dried coolant around the cap. I was pleasantly surprised with the easy fix and amazed that of all the sensors this car has, apparently it doesn't have one for low coolant in the auxillary reservoir.
05-10-2026
Have been keeping an eye on my secondary coolant reservoir - I see no leakage but I fill it to maximum and a few weeks/months later it's dropped a bit. I don't see any obvious leaking. Will have to pay closer attention to the cap.
X
05-11-2026
Change your oil asap and check for bearing material.
Could be nothing because of the heat + pissgas + altitude, or it could be bad news.
Yesterday
Make sure you check both coolant tanks to make sure they are full. I had that charge air temps too high error before and trigger a CEL before all due to the idiot dealership forgetting to refill the charge air coolant tank.
Superknock is always worrying to see. What i would do is change all plugs/coilpacks and do a blackstone labs oil analysis going forward. This should be something that is done anyway because it gives you true engine health report and can flag issues before something catastrophic happens.
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