Engine ground strap
Thread Starter
Member
Joined: Aug 2023
Posts: 120
Likes: 3
C300 15
Lets find out... 
LOGICAL:
You can use your favorite MB scanner to read module status
ELECTRICAL:
You can trace wiring with schematic to measure vitals: voltage and working bus
MISC:
What else are you considering?
You've got to start somewhere:
find leads from the essentials: PWR + GND + DTA
LOGICAL:
You can use your favorite MB scanner to read module status
ELECTRICAL:
You can trace wiring with schematic to measure vitals: voltage and working bus
MISC:
What else are you considering?
You've got to start somewhere:
find leads from the essentials: PWR + GND + DTA
Out Of Control!!
Joined: Apr 2019
Posts: 12,214
Likes: 6,897
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
shorts... not casual
Besides while connected, leaky sensor provides oil spread throughout the engine harness by capilllarity.
Thread Starter
Member
Joined: Aug 2023
Posts: 120
Likes: 3
C300 15
Out Of Control!!
Joined: Apr 2019
Posts: 12,214
Likes: 6,897
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Thread Starter
Member
Joined: Aug 2023
Posts: 120
Likes: 3
C300 15
another discovery, rhe fuse box gets 12.3 v from battery but the circuit 87 relay is only getting 11.79. Whats the problem here? Do I need a new fusebox
Out Of Control!!
Joined: Apr 2019
Posts: 12,214
Likes: 6,897
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
You're seeing a 0.5Volt drop!
This voltage drop is not directly bad for every circuits...
This won't stop your head unit from working.
There are a lot of distinct physical connections made between the 12.3 and 11.8 - Each connection is an opportunity for voltage drop and maintenance work.
I've been hunting voltage drops for years... the long story short here is you can focus on the SAM Relays cubes and the prefuse box internal connections. They are responsible for dropping voltages under load!
Furthermore...
-- Charge up main battery full (CTEK!) to have a more stable voltage that does not change under most loads.
-- Experiment disabling variable "ALT Opportunistic charging"... "Alt-LIN:OFF" to get a stable chassis power for ignition and injectors. This positively affects the engine learned maps.
Thread Starter
Member
Joined: Aug 2023
Posts: 120
Likes: 3
C300 15
Good catch
You're seeing a 0.5Volt drop!
This voltage drop is not directly bad for every circuits...
This won't stop your head unit from working.
There are a lot of distinct physical connections made between the 12.3 and 11.8 - Each connection is an opportunity for voltage drop and maintenance work.
I've been hunting voltage drops for years... the long story short here is you can focus on the SAM Relays cubes and the prefuse box internal connections. They are responsible for dropping voltages under load!
Furthermore...
-- Charge up main battery full (CTEK!) to have a more stable voltage that does not change under most loads.
-- Experiment disabling variable "ALT Opportunistic charging"... "Alt-LIN:OFF" to get a stable chassis power for ignition and injectors. This positively affects the engine learned maps.
You're seeing a 0.5Volt drop!
This voltage drop is not directly bad for every circuits...
This won't stop your head unit from working.
There are a lot of distinct physical connections made between the 12.3 and 11.8 - Each connection is an opportunity for voltage drop and maintenance work.
I've been hunting voltage drops for years... the long story short here is you can focus on the SAM Relays cubes and the prefuse box internal connections. They are responsible for dropping voltages under load!
Furthermore...
-- Charge up main battery full (CTEK!) to have a more stable voltage that does not change under most loads.
-- Experiment disabling variable "ALT Opportunistic charging"... "Alt-LIN:OFF" to get a stable chassis power for ignition and injectors. This positively affects the engine learned maps.
Last edited by Mercmiester; Yesterday at 06:29 PM.
Thread Starter
Member
Joined: Aug 2023
Posts: 120
Likes: 3
C300 15
Good catch
You're seeing a 0.5Volt drop!
This voltage drop is not directly bad for every circuits...
This won't stop your head unit from working.
There are a lot of distinct physical connections made between the 12.3 and 11.8 - Each connection is an opportunity for voltage drop and maintenance work.
I've been hunting voltage drops for years... the long story short here is you can focus on the SAM Relays cubes and the prefuse box internal connections. They are responsible for dropping voltages under load!
Furthermore...
-- Charge up main battery full (CTEK!) to have a more stable voltage that does not change under most loads.
-- Experiment disabling variable "ALT Opportunistic charging"... "Alt-LIN:OFF" to get a stable chassis power for ignition and injectors. This positively affects the engine learned maps.
You're seeing a 0.5Volt drop!
This voltage drop is not directly bad for every circuits...
This won't stop your head unit from working.
There are a lot of distinct physical connections made between the 12.3 and 11.8 - Each connection is an opportunity for voltage drop and maintenance work.
I've been hunting voltage drops for years... the long story short here is you can focus on the SAM Relays cubes and the prefuse box internal connections. They are responsible for dropping voltages under load!
Furthermore...
-- Charge up main battery full (CTEK!) to have a more stable voltage that does not change under most loads.
-- Experiment disabling variable "ALT Opportunistic charging"... "Alt-LIN:OFF" to get a stable chassis power for ignition and injectors. This positively affects the engine learned maps.
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Out Of Control!!
Joined: Apr 2019
Posts: 12,214
Likes: 6,897
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
These oil sensors are not too reliable with evidence of oil leaking through... Getting a new sensor was a good call.
Out Of Control!!
Joined: Apr 2019
Posts: 12,214
Likes: 6,897
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
The Steering Column has a module that benefits properly soldered connections. Direct your scanner to read SCM data... while gently turning side to side...
Neaby front footwells have shared GND posts many VIP Modules get referenced to. These GND deserved to be cleaned of the factory paint they got.
