No boost with jb4
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c43
No boost with jb4
Hoping I can get some help I have a 2019 c43 with a jb4 . I had it on for about 7-8 months then out of nowhere I would lose boost . I would have to shut the car off then back on again then it’s back to normal . Just recently it was so back the car shut off in traffic . At the time I didn’t think it was the jb4 but I had it at Mercedes 4 times with a total of 3 weeks altogether down time . They replaced everything including both turbos and spark plugs of course. The guys at bms sent me out a new board and having the same issue …. They did say it could be a misfire but there no way 2 sets of plugs are bad … I’ve tried every map and still the same
fyi : people say the jb4 can be detected if they dig deep but they actually flew someone out to look and work on my car (supposedly) and changed out the whole engine plus miscellaneous items so anyone thinking of a jb4 being detected I’m not so sure and my warranty is intact
fyi : people say the jb4 can be detected if they dig deep but they actually flew someone out to look and work on my car (supposedly) and changed out the whole engine plus miscellaneous items so anyone thinking of a jb4 being detected I’m not so sure and my warranty is intact
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From: Plainfield IL
Amg C43
Map 0 too?
tried logging while it happens?
I’ve had similar issues a few times
and just want to pull over to restart car as soon as I can.
this week engine light came on but jb4 read no codes
tried logging while it happens?
I’ve had similar issues a few times
and just want to pull over to restart car as soon as I can.
this week engine light came on but jb4 read no codes
Thread Starter
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c43
and no haven’t logged since it first started but it’s just weird how it worked fine for months and just switched up like that . Before all this happend I did send logs for map 6 and was told they were good by bms and after that never changed a setting or modified anything on the car. The dealer couldn’t figure it out either even after replacing anything
Last edited by godson960; Mar 31, 2023 at 07:50 AM.
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MBWorld Fanatic!
Joined: May 2021
Posts: 1,317
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From: Plainfield IL
Amg C43
That’s soooo strange.
Bad connector. Or frayed wire or loose pin but clearly it’s the connection of the jb4 unit. And so annoying
sorry man I hope things get figured out soon!!!
Bad connector. Or frayed wire or loose pin but clearly it’s the connection of the jb4 unit. And so annoying
sorry man I hope things get figured out soon!!!
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Member
Joined: Nov 2021
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From: New England Area
2015 ML63
Have you left the Jb4 unplugged from all connection points, reconnect original sensors. Same issue? I was running into this on my C43 but got rid of the car before I even looked into that issue i was having. do you know if they replaced the pressure transducer? Part number A000-153-18-00
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Joined: Mar 2017
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From: Omaha, NE
'16 AMG GTS, '21 AMG GLE53
This has intermittently been happening to me as well. I don't know what's causing it or a solution, but I did narrow down the point at which the boost drops off for me. Just after taking the onramp on the highway for my commute, somewhere within the first mile or so when I'm travelling between 70-77mph. Exact same thing...car drives fine, no codes, just no boost. Technically JB4 log shows .5-1.5psi under full throttle, but that's essentially nothing. A quick power down and start up and it comes back alive for the rest of the day. Some days it happens, most days it doesn't. Happened before switching to LEM intakes, and has persisted. Completely unpredictable when it happens though. 
MBWorld Fanatic!
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From: Omaha, NE
'16 AMG GTS, '21 AMG GLE53
Member
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From: New England Area
2015 ML63
It only happened to me after a hard launch at like 2400-2600 rpms i wanna say, not regularly driving around town. From what you said it sounds like a mile after the on ramp @ 70-77.. are you coasting up to those speeds are driving like you stole it n letting off?
Member
Joined: Jun 2019
Posts: 119
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From: Eastern,Washington
C450 & 335i 740whp
This has intermittently been happening to me as well. I don't know what's causing it or a solution, but I did narrow down the point at which the boost drops off for me. Just after taking the onramp on the highway for my commute, somewhere within the first mile or so when I'm travelling between 70-77mph. Exact same thing...car drives fine, no codes, just no boost. Technically JB4 log shows .5-1.5psi under full throttle, but that's essentially nothing. A quick power down and start up and it comes back alive for the rest of the day. Some days it happens, most days it doesn't. Happened before switching to LEM intakes, and has persisted. Completely unpredictable when it happens though.
Low boost/slow response fix for C43 C450 and the C400. Vacuum pump valve fix for M276 - YouTube
MBWorld Fanatic!
Joined: Mar 2017
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From: Omaha, NE
'16 AMG GTS, '21 AMG GLE53
Never happens in the middle of heavy acceleration…like maybe 5-10mph acceleration to pass or just pace away from someone. No more than 50% throttle I’d guess.
MBWorld Fanatic!
Joined: Mar 2017
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From: Omaha, NE
'16 AMG GTS, '21 AMG GLE53
Buy one of these vacuum valves next. If yours is gunked or failing You will start to get issues.
Low boost/slow response fix for C43 C450 and the C400. Vacuum pump valve fix for M276 - YouTube
Low boost/slow response fix for C43 C450 and the C400. Vacuum pump valve fix for M276 - YouTube
Member
Joined: Jun 2019
Posts: 119
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From: Eastern,Washington
C450 & 335i 740whp
Thread Starter
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Joined: Feb 2023
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c43
Have you left the Jb4 unplugged from all connection points, reconnect original sensors. Same issue? I was running into this on my C43 but got rid of the car before I even looked into that issue i was having. do you know if they replaced the pressure transducer? Part number A000-153-18-00
MBWorld Fanatic!
Joined: Jun 2012
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From: Toronto
2022 E53 AMG
In order to find out if this is part of the JB4, remove it from your car and plug in all the OEM plugs. Once you have done this, remove the power (negative) and let the car sit with the keys far from it so the modules all go to sleep. That will take about 15 minutes as they eat up any left over power in the system.
Now that your car is reset, drive it for the new couple of days. If the problem does not show again, then the JB4 is causing the problem however if the problem persist then the bad news is that your PCM is faulty.
Now that your car is reset, drive it for the new couple of days. If the problem does not show again, then the JB4 is causing the problem however if the problem persist then the bad news is that your PCM is faulty.
Thread Starter
Junior Member
Joined: Feb 2023
Posts: 20
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c43
In order to find out if this is part of the JB4, remove it from your car and plug in all the OEM plugs. Once you have done this, remove the power (negative) and let the car sit with the keys far from it so the modules all go to sleep. That will take about 15 minutes as they eat up any left over power in the system.
Now that your car is reset, drive it for the new couple of days. If the problem does not show again, then the JB4 is causing the problem however if the problem persist then the bad news is that your PCM is faulty.
Now that your car is reset, drive it for the new couple of days. If the problem does not show again, then the JB4 is causing the problem however if the problem persist then the bad news is that your PCM is faulty.
I actually did this 2 times once with all oem plugs plugged up and the 2nd time did the battery disconnected over night over a 5-7 day span cause I sent my jb4 back while I waited for my new board . The car runs fine and hard without the jb4 it’s scheduled for the dealer for 5th time if this doesn’t work corporate said a buy back or newer model is on the table . It sucks cause I really like the car
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From: Toronto
2022 E53 AMG
Okay, just don't tell them that you tuned your car.
If the car runs good without the JB4, I would agree, that is the issue. You are lucky you live in the USA because here in Canada, we would be stuck with the car and you can only send it back and forth, over and over again.
If the car runs good without the JB4, I would agree, that is the issue. You are lucky you live in the USA because here in Canada, we would be stuck with the car and you can only send it back and forth, over and over again.
