Installed amp and subwoofers. Having issues a couple weeks after install?
Thread Starter
Newbie
Joined: Jun 2024
Posts: 6
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2019 W205 C300 4matic
Installed amp and subwoofers. Having issues a couple weeks after install?
Good day everyone, a few weeks back a friend helped install a 1,200 watt Kicker amp and (2) 12" Kicker subs in my 2019 C300. I had no issues for the first couple weeks. One day the car was idling for 45 minutes to an hour and after I drove off, within a few miles I had Blind Spot not functioning pop up on my dash. It continued to come and go until a couple days later the Battery Do Not Turn Off Engine came up on my dash. I hooked a charger up when I got to my destination that day and replaced the battery the following day. Now, when I start it everything is as normal but within 5 minutes of driving I'm getting multiple warnings on my dash. Braking Assist limited, Blind Spot not functioning, Do not Shift, Apply parking brake....I unhooked and removed the amp and subs but I get the same warning. Also they immediately came in when I revved the engine in the driveway last night? Thanks in advance for any help
MBWorld Fanatic!
Joined: Feb 2017
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From: Baltimore County, MD
'13 s212 63 p30. '06 LX470
Good day everyone, a few weeks back a friend helped install a 1,200 watt Kicker amp and (2) 12" Kicker subs in my 2019 C300. I had no issues for the first couple weeks. One day the car was idling for 45 minutes to an hour and after I drove off, within a few miles I had Blind Spot not functioning pop up on my dash. It continued to come and go until a couple days later the Battery Do Not Turn Off Engine came up on my dash. I hooked a charger up when I got to my destination that day and replaced the battery the following day. Now, when I start it everything is as normal but within 5 minutes of driving I'm getting multiple warnings on my dash. Braking Assist limited, Blind Spot not functioning, Do not Shift, Apply parking brake....I unhooked and removed the amp and subs but I get the same warning. Also they immediately came in when I revved the engine in the driveway last night? Thanks in advance for any help
Thread Starter
Newbie
Joined: Jun 2024
Posts: 6
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2019 W205 C300 4matic
Did you replace the accessory battery as well? Many of the functions you mention are through accessory power. Do you know which battery circuit was used as power. It sounds like you are discharging something that isn’t recharging. Have you put a meter on the battery while running to check the alt?
MBWorld Fanatic!
Joined: Feb 2017
Posts: 2,296
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From: Baltimore County, MD
'13 s212 63 p30. '06 LX470
Thanks so much for taking time to respond to my post. I did order a new auxiliary battery and it's being delivered today. I'm working a 14 hour day today so I won't have a chance to install it till tomorrow. I'll certainly update you after the new ones in whether it fixes it or not and it may help someone else in the future with a similar problem as well. Hope you have a great day!
Thread Starter
Newbie
Joined: Jun 2024
Posts: 6
Likes: 1
2019 W205 C300 4matic
I installed new auxiliary battery and we checked all fuses in the trunk but I will check the fuse again. No difference at all. Drive for several minutes and everything lights up and goes into limp mode. Scanner faults all say communication lost with pcm and implausible message? I have been sick and stuck in bed last several days.
Newbie
Joined: Jan 2026
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From: United Kingdom - Kent
W205 2016 RWD C200
Have you resolved the issue?
Did you check your voltage at idle 12v and engine running at 14v?
How did you connect your amplifier and sub / woofers?
Did you check your voltage at idle 12v and engine running at 14v?
How did you connect your amplifier and sub / woofers?
Last edited by RomeoS; Jan 6, 2026 at 12:45 PM.
