Advice needed
Thread Starter
Newbie
Joined: May 2026
Posts: 7
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Advice needed
C63s limp mode at highway cruising.
So as of 2 months ago bought a 2017 c63s estate. 60k kms. Stage 2 tune with 560 wheel hp
Ive been dailying it and put about 6 thousand km on it (95% highway).
2 days in a row the car has been doing 115, cruise control on, the car seems to shutter/stutter and then all the electronics modules seem to fail and turn off. I get the standard E-diff message as well. Car goes into limp mode, which goes away after I restart the engine.
Yesterday I took it to a mechanic and the only significant code it threw was a low voltage code. I replaced the battery as it was at 70%health.
Today it happened again in almost the same circumstances. The check engine light stayed on for afew restarts and now the car looks and feels normal. My mechanic wants to keep the car for a day or 2 to diagnose but im worried it might be difficult to reproduce the intermittent problem
Im a bit lost as to what it could be, has anyone here dealt with this before?
Ive included the diagnostic as well from before the battery was changed
Thanks in advance
So as of 2 months ago bought a 2017 c63s estate. 60k kms. Stage 2 tune with 560 wheel hp
Ive been dailying it and put about 6 thousand km on it (95% highway).
2 days in a row the car has been doing 115, cruise control on, the car seems to shutter/stutter and then all the electronics modules seem to fail and turn off. I get the standard E-diff message as well. Car goes into limp mode, which goes away after I restart the engine.
Yesterday I took it to a mechanic and the only significant code it threw was a low voltage code. I replaced the battery as it was at 70%health.
Today it happened again in almost the same circumstances. The check engine light stayed on for afew restarts and now the car looks and feels normal. My mechanic wants to keep the car for a day or 2 to diagnose but im worried it might be difficult to reproduce the intermittent problem
Im a bit lost as to what it could be, has anyone here dealt with this before?
Ive included the diagnostic as well from before the battery was changed
Thanks in advance
Last edited by Wolfman; Jun 4, 2026 at 07:26 AM.
Senior Member
Joined: Dec 2025
Posts: 483
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From: Keep it simple - keep it OEM
AMG C63s Coupe
Hello @Jw c63s
what year & miles is your car ?
bad battery i dont know … While you were driving, the alternator was working too.
Whats that for pdf ?
Make screenshot and put it as picture in thread.
what year & miles is your car ?
bad battery i dont know … While you were driving, the alternator was working too.
Whats that for pdf ?
Make screenshot and put it as picture in thread.
Thread Starter
Newbie
Joined: May 2026
Posts: 7
Likes: 1
Hello @Jw c63s
what year & miles is your car ?
bad battery i dont know … While you were driving, the alternator was working too.
Whats that for pdf ?
Make screenshot and put it as picture in thread.
what year & miles is your car ?
bad battery i dont know … While you were driving, the alternator was working too.
Whats that for pdf ?
Make screenshot and put it as picture in thread.
69*** km. So 40ish thousand miles
the battery was 10 years old oem from merc. It was probably due soonish anyway
Thread Starter
Newbie
Joined: May 2026
Posts: 7
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Thread Starter
Newbie
Joined: May 2026
Posts: 7
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Senior Member
Joined: Dec 2025
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From: Keep it simple - keep it OEM
AMG C63s Coupe
@Jw c63s have you also replaced the "auxiliary battery" in the passenger foot well? (it's actually more of a capacitor).
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Thread Starter
Newbie
Joined: May 2026
Posts: 7
Likes: 1
@Jw c63s have you also replaced the "auxiliary battery" in the passenger foot well? (it's actually more of a capacitor).
Here's a video on it:
https://youtu.be/qiLLqjqyNoM?si=Cj644qPI2lZAE1nA
Here's a video on it:
https://youtu.be/qiLLqjqyNoM?si=Cj644qPI2lZAE1nA
Ive been driving the last few days and have had nothing new happen. In my brain these limp modes happened when I had driving assists on and cruise control. Is it possible the computer just ran out of RAM or something? I have no idea if my theory is stupid or not.
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Joined: Jan 2024
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From: Colorado
2018 C63S AMG Coupe, 2019 Jaguar F-Pace SVR
The low / bad primary battery is frequently the cause of strange behaviors like multiple faults and limp mode. If you have replaced the battery, cleared the faults, and all is well, then I'd leave it alone. If the electrical gremlins reappear then maybe investigate whether or not your car has the auxiliary battery and try replacing that.
Thread Starter
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Joined: May 2026
Posts: 7
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So update. It hasn't gone into limp mode since. Yet when I drive it hard at all I seem to get the Ediff message. Also afew times when driving it hard, all the warning lights on the screen flash.
Tonight it did this and gave me a message "take the car to workshop without changing gear". This message went away shortly after.
During that drive I tried to enable cruise control and it told me that the module was unavailable. Which makes me think its some type of computer or ECU issue.
Im taking the car to the mechanic on Thursday so will keep anyone interested posted.
Thanks for your advice
Tonight it did this and gave me a message "take the car to workshop without changing gear". This message went away shortly after.
During that drive I tried to enable cruise control and it told me that the module was unavailable. Which makes me think its some type of computer or ECU issue.
Im taking the car to the mechanic on Thursday so will keep anyone interested posted.
Thanks for your advice
