Mercedes-Benz C63 Random Power Loss Explained
If your Mercedes-Benz C63 AMG is feeling a little sluggish, you may be in ‘limp mode’ without even knowing it.
A few months back, MBWorld member amg8 posted in the C43 AMG, C63 AMG, C63S AMG (W205) about how his 2017 Mercedes-Benz C63S AMG felt like it was low on power. He points out that it was fine for a while, but when he made the post, the car just didn’t feel like it had as much power as it had when he first got it.
“So I am driving a MY17 C63s and when I first got it, all the power is there. On the freeway at around 65mph, I can floor it passed kickdown and the wheels would chirp in Sport+.
Recently I feel the loss of power. It just doesn’t pull as hard as it used to and no it is not because I got used to it.
I can see the on screen HP and TQ and it would both hit at max but only for about 2 full seconds and it would start to decline. It didn’t use to do that.
I have not gotten any updates to my ECU so that is not it.
Not sure if anyone else had experienced this?”
MBWorld member mayzo was the first to respond, explaining that he has experienced this issue with his C63S and knows why:
“This sounds like what happened to me when the battery was drained while the car was being detailed. When the battery is low it puts the car in a sort of limp mode and feels like driving with the emergency brake on (especially in first and second gear).
I can also be caused if you leave the key fob in the car for long periods of time, leave the lights on or door open.
The only way to fix this is have the dealer or Mercedes mechanic reboot all the systems.”
The thread is then populated by some back-and-forth with some members insisting that it cannot be a voltage issue when MBW member munis shared his own experiences – echoing the input of mayzo:
“What you are describing is exactly what I experienced as well and it is exactly like what Mazyo is talking about. Both of you are talking about the same thing. The car is in a limp mode. May be you did not drive the car for a while and the battery was low, so the car entered a limp mode. Only way to get rid of it is have the dealer access your ECU and TCU and reset all the systems. All of them.
This fixed it for me. Also this is not caused only by a low battery. If your ECU has any secondary error codes (codes that are there but does not cause check engine light), some of them might trigger limp mode as well.
I know exactly what you are talking about. Happened to me last week as well. It is all fixed now. My car was putting down 100hp less and 150 trq less than the regular numbers I am used to.
I will upload a video when I can.”
He also added this later in the thread:
“I will be posting my work order here. This basically fixed it. This is caused by low battery in the car and it basically goes into a limp mode. So you have to reset all the systems in the car separately and then it goes away. Have seen several people with the same problem. I think this a very simple fix for all of you guys.”
Unfortunately, the OP went to his dealership and they werent able to help:
“Just to give an update here. After taking in the car, the dealer hooked it up to their diagnostics and said there were no updates available and that the car has the latest software. So basically there is nothing they can do for me.”
The Problem Solved
However, amg8 was eventually able to cure the low-power-problem with his C63S via with the help of a certified local Mercedes mechanic:
“Ok here is the verdict at least for me. After months of dealing with this and trying different things I finally went to a local merc mechanic thanks to Mazyo! When they hooked it up to the system ( I presume Xentry ) they found miscommunication between the ECU/ME causing lowered performance. At that time I asked them why didn’t the dealer tell me this when I took it in and they just shrugged and said it is possible they didn’t want to do anything with it or didn’t really look.
So to shorten the story, after they “reprogrammed” the ECU/ME, all my power is back. He said he has seen many 63s with this same issue due to low voltage tripping the “limp” mode and said once that fault code is registered, it has to be removed/reprogrammed to have it reset.
At the time ( earlier in this thread ) I thought to myself low voltage couldn’t be an issue with my car but then it hit me. I have two Cellink B batteries that powers my dashcams and it charges when the car is ON. So I am guessing a couple of times when I went to get carwash, they must of left the ACC ON and that will trigger the charge and thus drained part of my battery enough to trigger a low voltage fault.
So my recommendation to you if you have this similar issue is take it to several mechanics if one says nothing is wrong ( like they did to me at the dealer ). My second recommendation is if you have many accessories like hardwired radars and dashcams even if they’re only ACC HOT, invest in a deep cycle battery. I would recommend the Optima Yellow Top but they don’t make ones that fit our cars last time I checked so perhaps the Duralast Platinum AGM battery would be the next best one which does fit our cars.
In closing mystery solved! At least for me.”
So, if you have a Mercedes-Benz C63S AMG which feels like it is falling short of 500+ horsepower, you might be running into the same issue described at length in this thread.
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