Shifting From Park
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From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
Shifting From Park
I wanted to start this thread as there is an understanding amongst members that the AUX battery is in place to be able to shift transmission from PARK if engine fails to run. I was one of these members but I have learned differently with my two MB cars I currently own.
I have tested for this and in both my 2010 E550 and 2013 S550 I cannot shift gear from PARK if the engine is not running, period. If engine does not run the tranny will not change from PARK in either of my cars. And batteries are good.
Would there be an expert word in the forum to put facts on this as I think it is misinformation that aux battery allows switching from PARK if engine fails to run.
I have tested for this and in both my 2010 E550 and 2013 S550 I cannot shift gear from PARK if the engine is not running, period. If engine does not run the tranny will not change from PARK in either of my cars. And batteries are good.
Would there be an expert word in the forum to put facts on this as I think it is misinformation that aux battery allows switching from PARK if engine fails to run.
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From: 122W, 37N
2016 E350 4Matic wagon, 2019 Ford Expedition, 2019 Chevy Bolt EV
ok, I was able to put my 2016 4matic that has the pushbutton start/stop into N without the engine. first, press the START button *without* stepping on the brake, this turns the car on without starting the engine. THEN step on the brake, push the shifter down to "D", then up to "N" and its now in N and wanted to roll backwards if I eased up on the brake.
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From: SoCal. Desert
'16 E350, gone: '03 c230k
ok, I was able to put my 2016 4matic that has the pushbutton start/stop into N without the engine. first, press the START button *without* stepping on the brake, this turns the car on without starting the engine. THEN step on the brake, push the shifter down to "D", then up to "N" and its now in N and wanted to roll backwards if I eased up on the brake.
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Thread Starter
MBWorld Fanatic!
Joined: Oct 2010
Posts: 5,141
Likes: 1,293
From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
ok, I was able to put my 2016 4matic that has the pushbutton start/stop into N without the engine. first, press the START button *without* stepping on the brake, this turns the car on without starting the engine. THEN step on the brake, push the shifter down to "D", then up to "N" and its now in N and wanted to roll backwards if I eased up on the brake.
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From: Pepper Pike Ohio
24 GLS580 '23 E450 4matic 12 E350 4Matic
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From: Dallas-Ft.Worth,TX
2016 E350 Sport
And... I don't think anyone has determined what each battery does, either. Educated guesses, yes, but not definitive information.
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From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
Just verified this works in my S560. I’m sure it works the same way in the E550.
Very good info as if the car needs to be towed just on the flat bed it can be without dragging the wheels on ground, which was done once to my E550 when it would not start. Tow truck did not have the reverse spinning wheel to install so rear tires we dragging on drive way. With this info it gets a lot easier.
Thanks again!
Very good info as if the car needs to be towed just on the flat bed it can be without dragging the wheels on ground, which was done once to my E550 when it would not start. Tow truck did not have the reverse spinning wheel to install so rear tires we dragging on drive way. With this info it gets a lot easier.
Thanks again!
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From: Pepper Pike Ohio
24 GLS580 '23 E450 4matic 12 E350 4Matic
True enough, I certainly don't mean to portray myself as an expert, with extensive searching, I still can't find a definitive answer what the function of the 2010-2013 in-dash battery is specifically, nor can I find what the specific function of the in-trunk battery in the 2014-2016 models
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From: 122W, 37N
2016 E350 4Matic wagon, 2019 Ford Expedition, 2019 Chevy Bolt EV
traditional car electrics, with a single starter battery, the system voltage often drops as low as 9V when you start the car due to the massive current drain by the starter motor... this disrupts all sorts of electronics. high current things like stereos, lighting, ventilation fan were traditionally put on a 'load shed relay' that was shut off when the starter was engaged to let the battery supply maximum power to the engine during this start.
the SAM cuts all that stuff over to the aux battery so the lights do NOT have to be shut off during a start or restart, so the stereo and navigation computer don't have to be reset, etc. also so low system voltage to the engine control computers doesn't cause problems.
the SAM cuts all that stuff over to the aux battery so the lights do NOT have to be shut off during a start or restart, so the stereo and navigation computer don't have to be reset, etc. also so low system voltage to the engine control computers doesn't cause problems.
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2011 E-350 4Matic Sport
True enough, I certainly don't mean to portray myself as an expert, with extensive searching, I still can't find a definitive answer what the function of the 2010-2013 in-dash battery is specifically, nor can I find what the specific function of the in-trunk battery in the 2014-2016 models
The WIS diagram for my car shows the aux battery G1/7 connected to left footwell ground W15/5 and to fuse F1/1f1 at the front SAM N10/1 which also includes a relay module and voltage sensor. Voltage is routed from the SAM to (1) the ignition switch module N73 and (2) transmission control module U490. Makes sense if it's needed for column shifter operation when the main battery is dead - allows ignition to unlock and for shifter to be operated. Charge voltage determination was as mentioned through the SAM module that senses voltage from the aux battery and increases charge if needed. The WIS shows the aux battery as a separate circuit independent of the main battery circuit, and it would appear that charge voltage (engine running) would be sent back to the aux battery via the SAM as it's very low amperage (small ga wiring) involved.
Its also possible that through the ignition switch connection the aux battery supports cluster and lighting - I haven't checked that. But I'm going to look at the diagram for the ignition switch and module and see how voltage is routed.
For the later models with ECO, keyless, etc I don't doubt that the larger trunk aux battery has more support duties in the vehicle than in my particular year.
Last edited by Mud; Jan 27, 2021 at 04:43 PM.
Thread Starter
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From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
I had posted this in another thread on my non-ECO, non keyless go 2011. I think the WIS wiring diagram is pretty clear:
The WIS diagram for my car shows the aux battery G1/7 connected to left footwell ground W15/5 and to fuse F1/1f1 at the front SAM N10/1 which also includes a relay module and voltage sensor. Voltage is routed from the SAM to (1) the ignition switch module N73 and (2) transmission control module U490. Makes sense if it's needed for column shifter operation when the main battery is dead - allows ignition to unlock and for shifter to be operated. Charge voltage determination was as mentioned through the SAM module that senses voltage from the aux battery and increases charge if needed. The WIS shows the aux battery as a separate circuit independent of the main battery circuit, and it would appear that charge voltage (engine running) would be sent back to the aux battery via the SAM as it's very low amperage (small ga wiring) involved.
Its also possible that through the ignition switch connection the aux battery supports cluster and lighting - I haven't checked that. But I'm going to look at the diagram for the ignition switch and module and see how voltage is routed.
For the later models with ECO, keyless, etc I don't doubt that the larger trunk aux battery has more support duties in the vehicle than in my particular year.
The WIS diagram for my car shows the aux battery G1/7 connected to left footwell ground W15/5 and to fuse F1/1f1 at the front SAM N10/1 which also includes a relay module and voltage sensor. Voltage is routed from the SAM to (1) the ignition switch module N73 and (2) transmission control module U490. Makes sense if it's needed for column shifter operation when the main battery is dead - allows ignition to unlock and for shifter to be operated. Charge voltage determination was as mentioned through the SAM module that senses voltage from the aux battery and increases charge if needed. The WIS shows the aux battery as a separate circuit independent of the main battery circuit, and it would appear that charge voltage (engine running) would be sent back to the aux battery via the SAM as it's very low amperage (small ga wiring) involved.
Its also possible that through the ignition switch connection the aux battery supports cluster and lighting - I haven't checked that. But I'm going to look at the diagram for the ignition switch and module and see how voltage is routed.
For the later models with ECO, keyless, etc I don't doubt that the larger trunk aux battery has more support duties in the vehicle than in my particular year.
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From: Fredonia, WI
2012 E550 v8-Biturbo
Thanks. This is good info
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From: 122W, 37N
2016 E350 4Matic wagon, 2019 Ford Expedition, 2019 Chevy Bolt EV
of course, the SAM is just a big black box, there's no documentation on how exactly they respond to various external states, so its hard to say when exactly any given output gets powered by either or both batteries.
