This kind of fault is a bugger to find and repair. I'm still leaning toward a poor ground or poor connection through a ground lug (or maybe even a loose ground post that is mounted on the car body). Wiggle the wires that are crimped within a ground lug to ensure they do not move within the area of the lug that is compressed onto the wire. If the wire can move within the crimp, its connection is likely poor and this can lead to low voltage readings on electronic components (because there is a voltage drop at the crimp, thus "stealing" voltage from the electronic components it provides a ground for).

Remember:

• current leaves the battery or alternator & goes to a fuse
• current goes through, & leaves the fuse & goes into a wire
• goes through wire
• enters an electronic component
• goes through the component
• exits the component
• returns to the voltage source's return point

if there is a high(er) impedance point in any of the wires or connectors (ground connectors included), there will be a voltage drop across that point - meaning there will be less voltage across the component being supplied with voltage. The total voltage at the fuse will be correct, but some loss will appear across the poor connection in the circuit. Vibrations in driving can make a loose connection work sometimes, and sometimes not.

Suggest to re check the ground connectors that were previously cleaned and gave good results for a short time. Also, check any others that you can find. The wires may be loosely crimped within those ground lugs. Simply compress the crimped area a little more. If it won't tighten, replace the lug.

Same rules apply for connectors in wiring harnesses.

By the way, how conductive is the fluid that is leaking when you unplug the wire? Maybe that's the problem - a connection to a ground point through the fluid.

Hope that helps a bit (been here many times in previous life ).

 

Unfortunately charge cycle history was not checked, only an alternator & load test which gave no result other than a suggestion of replacing the battery as the test would only run with a spare battery at the shop & not my (then) near 4 yr old battery. Foolishly, I did replace the battery knowing it would likely solve nothing.

I can't say for sure which version of Xentry they are running, but I'll find out. Thank you for bringing this to my attention. I do feel partially blind without Xentry, especially for testing. I've never had my hands on such a tool & was hoping I wouldn't need to until some point in the distant future to be honest! I'll be checking in with them again as I also do some more Xentry homework, even if I don't end up getting a rig just yet.

 

This is absolutely excellent and helps a lot. Many thanks! Since I have just revisited all GND points last weekend, as suspected the front L wheel well ground (which is the TCM's ground) had corrosion return to it. Not as significant as when 1st inspected a yr ago, but certainly at the level of concern. When checking for battery voltage at this ground, the reading was good everywhere except for the wire itself coming out of the crimp. I did wiggle all grounds and didn't see/feel excessive play, but this I will recheck again in the coming days. I also detected no voltage drop there at rest, with IGN on, or while running. However, I'll also check these again because 2 days prior to cleaning grounds again I maintained a steady 14.2 - 14.9v so I was not in a consistent state regarding this entire debacle.

To your point, yesterday I did see 12.4 - 12.5v at the fuse, but 11.8 & as low as 11.3v from the TCM via iCarsoft MB V2. Is this more evidence for your case? I certainly hope so. I would also like to inspect the connections at the front SAM itself, especially given the fact I've had consistent Historic CGW faults regarding shorts to GND, POS, and/or CAN network unstable during all this. The front SAM is always the common denominator in every fault in this "adventure".

I can't speak to the conductivity of the trans fluid, but will certainly look into it. I was concerned of it wicking itself into the front SAM as I am clueless how long it had been leaking (but assume it's only been a few months corresponding to the beginning of these issues.)

What's most strange about that is last weekend I went to inspect the TCM connector for the 3rd time, and it was BONE dry! 1st visit = fluid poured out. 2nd visit = noticeable amount of fluid residue, but maintained somewhat clean appearance from last cleaning. 3rd visit = spotless. Did I slightly overfill during my last fluid/filter service? (Just over a yr ago). I imagine the connector is not the path of least resistance, or is it? You have given me balance, as electrical work has been in the same category as my willingness to eat broken glass for dinner (at this level at least), but the logic and order in your breakdown has my perspective changing. Much appreciated.

 

@S-Prihadi , what a wealth of knowledge and information! I must say, your willingness to dive in hands on and fully address a topic shows a great passion and even an artistry that my musician brain can relate to. It is an interesting thing to see passion, artistry, cohesiveness, mechanical knowledge, electrical knowledge, and perseverance all intersect (as is also the case with most others on MBWorld).

I appreciate this very much. I must sit with this info and make sure I digest and carry it out properly. I will return!

 

If W207 Front SAM is similar to W212, that connector 9G would be similar to this one :

.

Below : F21 to F31 is the coordinate of fuses in the diaghram. Fuse I will write as Fuse 33.



.




Your Front SAM 9G connector, pin 2 would be 1.0mm red with black tracer, mine is Red with white tracer.

.




I hope you do not need to go to the extend of removing Front SAM to take a look at its connectors, its not a fun prospect.
I have removed mine to do conformal coating on it and to catalog all its 138 wires.


.
The Front SAM 10 pages wiring diagram for my car, has a few mistakes. So you also should be ready when and if you ever remove the Front SAM.
I do all these for future use ( I am keeping the car to minimum 20 years of age ). Understanding your car when everything is working normal is a good database, as you are not under pressure.



Knowing wire colors and size at Front SAM does not guarantee there is no interconnection in the middle of the destination and wire color may change at final destination module.
Not all interconnection is noted in the WIS.

Here are 2 interconnectors I can't find any data on it in WIS. It could be for RHD car only. These wires and connectors are inside the fuse box housing the Front SAM.
See how the wire color change, on some.

.



.


.



.


Fuses with white tape label of its amperage, those are fuses NOT IN USE for my car, thus they become spare fuse when needed.
Fuses with strings are fuses located so deep under the wiper motor arm, its very difficult to pull out, thus I drill them and place a string for ease of removal


Above : shiny female pins are what "grab/bite" your fuses and relays male pins.


------------




.



.



.


Wiper arms/assy for RHD W212 need to removed to access Front SAM motherboard.


Horrible working location for those fuses near firewall, hence the strings are used. LOL

.

 

Before you go down the wormhole and rip your car apart looking for a one in a million problem,
this may help you ( or your shop)
https://automotivetechinfo.com/2019/...-that-battery/

These types of issues typically turn out to be something basic that is missed in the initial diagnosis process.

Haven’t looked at the WIS for your car, nor have I run it in simulation mode for your VIN yet, but going from memory.
(simulation mode doesn’t always show all available functions/tests either)

Does your car have the Aux battery behind the dash?

Depending on year/model/engine, you may not have access to the same functionality as shown in the article&thread above.

It also appears (as you can see in the linked thread I posted) not everyone can access this depending on their version of XENTRY.

Good Luck

 

S-Prihadi's pics reminded me of something else.

The connector headers (the plastic housing that holds the wires and their individual connector pins) can hide a fault that we don't often think about. We can press the headers together to connect the wires together, and it looks like good connections are made within the headers. An individual female pin may not hold its male counterpart tightly resulting in an unreliable connection. Check for voltage drops across the pins - for example, measure voltage across the pins (while connected) on matching colour wires (for example, the green wire, then the blue wire, etc.). Wiggle the wires to see if there is any change.

It is difficult to tighten the "grip" of a female pin, but it can be done. If possible, it is best to replace the pin, but you will need a special crimper to crimp a new pin on the wire.

If you need to fix a poor crimp on one of the pins, it can be difficult to get a pin out of the header. There are special tools for this, but you might have success with your own tools to gently remove a pin. Be very careful, as it is relatively easy to damage a pin or the housing - then you're really stuck.

When you get to this level of difficulty, it's best to let someone who has the pins and the tools do the job unless you have done this before.

Above is a screen shot of a random Amphenol pin. The point leaves on the right wrap around the wire to hold it to the wire body physically, the wide leaves are rolled over and pressed into the bare copper wire with a crimper. This is the point where some crimps are not tight. Pins similar to this are used in the headers shown in S. Prihadi's pics. The little wedge sticking out below is what holds this one in a header.

Anyway, enuf blathering from me

 

Just to follow up,
ran XENTRY simulation with your VIN, looks like you (shop) should have access to the LIN-BUS battery diagnostics.
It’s there, shop has to figure out how to access it. Parasitic drains should show up, along with clues to responsible circuit.
Simulator won’t show stored cycles, as there are none.

see XENTRY screen pic below with your VIN & accessible data screens.
My advice, stick to basics in diagnostics first, there’s always time to go down the wormhole

Good Luck!

 

I apologize for my delay. If it weren't for the fact that this car is nearly mechanically perfect & I know exactly where everything stands (except for the issue of this thread), then I would be at peace with selling the car broken. But my one mechanical nightmare which is left is the rear arms. All of them. This job I dread, especially for the lack of information on it, but I cannot sell a mechanically and electronically broken car that theoretically is almost "done".

I can't thank you enough for this SAM write up. I am thinking I have no choice but to inspect the 9g connector. I have tested fuse 33 amperage via the Fuse Buddy device & I observed a constant 2.2 - 2.5 amp draw regardless of P, R, N, or D. The voltage does increase in R, but amps were consistent. I also instantly got a 2.3 amp draw with IGN ON.

I've found mo other oddities anywhere else. No voltage drops, no high resistance, all GND's clean and tight. No circuits are staying on (that I've found). No play anywhere as far as from a GND lug, stud, or crimped connections. The only place where I observe low voltage is from TCM module via iCarsoft. 11.3 - 11.8 while driving, occasional blips of 12v. 12.8v or so while in R.

I cleared the code (which now is only 0705 Selection range sensor defective causing the CEL) & did data logging to see what happens when it returns. Unfortunately I need a Windows machine to print the data & I just have Mac! I will have one soon though. However, I can say the fault 95% of the time has come when I am at constant highway speed for at least a few minutes.

Unfortunately I don't have anything to do load testing with. Anything specific you recommend? I would also like to start doing some back probing of the TCM connector and perhaps the 9g connector at front SAM. Besides this, I think Xentry will do better than me looking for needles in haystacks. I thank you again. Still many of your wiring diagrams to review as well.

 

Many thanks for this and your post just before this!! Enormous help and exactly the route I'm looking for at this stage. I certainly have no desire whatsoever to enter the wormhole. I like to keep my wormholes theoretical and fun, like thinking about time travel and parallel dimensions rather than an undiagnosed electrical mess!

Aside from inspecting the front SAM connector & possibly some back probing, there's not much else to do without a proper Xentry session. If I were to get my own Xentry rig, is there a route you'd recommend for a DIY'er? I also look after my sister's W203 ('07 C230 Sport) & personally never plan to own anything newer than 2011 (unless an M156 car came into the picture). My plan was actually to sell this car & get into something Bruno Sacco, but then this issue came along.

Also forgot to mention in earlier posts (if it's an indicator of a specific course of action), I have relays clicking loudly from the front SAM when I unlock the car from cold. Not 100% of the time, but at least 70-80%. If not relays clicking, it will be an audible electrical click from the battery area itself. Also, if car is off for a few mins and I am under the hood, I hear relays clicking. Not rapidly or excessively, but noticeably. Perhaps the latter is normal? I did swap the horn & circuit 87F (relay R for TCM & Fuel control module) at the beginning of all this & naturally it made no difference.

Just trying to include everything I can at this point regardless of how big or small. I've also watched selection of gears, etc via live data with the CEL on & off, both times no anomalies were observed. I have had a few very harsh slips into N while pulling away from red lights (twice) but no other drivability symptoms. I've also observed under the "Emergency Mode" section of the TCM in iCarsoft that it said there was a fault when the CEL was cleared while another time it said there was no fault when the CEL was on & fault 0705 was current (along w/ it's friend 0688 in the ECU).

 

[/QUOTE]
The connector headers (the plastic housing that holds the wires and their individual connector pins) can hide a fault that we don't often think about. We can press the headers together to connect the wires together, and it looks like good connections are made within the headers. An individual female pin may not hold its male counterpart tightly resulting in an unreliable connection. Check for voltage drops across the pins - for example, measure voltage across the pins (while connected) on matching colour wires (for example, the green wire, then the blue wire, etc.). Wiggle the wires to see if there is any change.

If you need to fix a poor crimp on one of the pins, it can be difficult to get a pin out of the header. There are special tools for this, but you might have success with your own tools to gently remove a pin. Be very careful, as it is relatively easy to damage a pin or the housing - then you're really stuck.

When you get to this level of difficulty, it's best to let someone who has the pins and the tools do the job unless you have done this before.
[/QUOTE]

This is high in my list of concerns indeed. Unless someone has been under the front SAM for some ungodly reason, I can't imagine how or why I would have problems with the pins or connectors. Along with what you've shared, the fluid leak has me thinking it'd be foolish to not examine. I still don't understand how this leak has simply stopped, but I am thankful!

I have only de-pinned my side marker wiring over a yr ago to fix a water ingress mess there. This front SAM or TCM connector I would happily leave to someone else if it got to that point! Thank you for this @KanataSteve

 

You wrote in green :
I have tested fuse 33 amperage via the Fuse Buddy device & I observed a constant 2.2 - 2.5 amp draw regardless of P, R, N, or D.
The voltage does increase in R, but amps were consistent. I also instantly got a 2.3 amp draw with IGN ON.

Your result is a bit different than mine.
ENGINE OFF -IGNITION ON , Mine has lowest current during P , N and D and highest in reverse, yes I can't do gear 1 or 2 manually with my drive shaft removed.

Ignition ON engine OFF thus TCM is on = 1.2 amps
Park, Neutral, D = still 1.2 amps
Reverse = 2.2 amps
Again this is engine off and solenoid does not fight oil pressure and torque converter solenoid is proabably not activate. I assume your test is also engine OFF ignition ON only..... yes ?
NOTE : This difference could be because your conductor plate or TCM computer is VGS3 and mine is VGS4.

The good thing is , 2.2 amps will not kill 1.0mm wire.


-----------------

You wrote : The only place where I observe low voltage is from TCM module via iCarsoft. 11.3 - 11.8 while driving
If your alternator LIN is still connected and the ECM is still controlling alternator , I am not suprised to see as low as 11.3V at the TCM during driving,
because your car system voltage can be as low as 12.1V. However, I believe a low voltage DTC if any at TCM is an issue if 11V or lower. That is what N93 Front SAM gateway claim as low voltage, 11V.
I also read in 1st post that you ALT-LIN is disconnected, but you are not getting as good steady 14V voltage like most of us with ALT-LIN removed.




N93 gateway is a second computer residing inside N10/1 Front SAM. So N10/1 front SAM is dual processor and duty.
Scanner can read N93, but there is no wiring information specific for it, it uses N10/1 Front SAM wiring.


-----------------

I think you should not worry about voltage drop up to 1 volt at modules, based on X voltage of the car system at that point in time.
It is inevitable for voltage drop to happen, within limits of course.....due to load and distance and connectors and small wire size used.
Your COM issue at TCM was probably due to the oil at connector and now all good.

-------------------

If you want to have stable 14V and smart low amps charging by the alternator when battery is full, this will be a better focus.
Your alternator is supposedly P/N A0009061102 and is only 150 amps COLD.


If heat soaked and at idle of 550 RPM in D while braked, I do not think it can produce more than 45 amps.
550 RPM in D braked hold is my engine, yours could be 600-650 RPM.
I am on a 200A Valeo.

If mounting frame is the same and pulley match, you can use W212 E350 M272 alternator of 180A.








One thing to note, the Alt-LIN unplugged been very successful on Valeo alternators, must check members who are on Bosch M272 E350 180A and alt-lin un-plugged, see their result.
Alternator design and the voltage regulator design will dictate how good the alternator charging and amperage output profile is and how good at low engine RPM.
180A or 150A or 200A alternator can only produce the said amount if the alternator itself spin 3,000 RPM. Heat soak can reduce alternator output by 20%.
You can do the pulley ratio math between alternator and main crankshaft damper pulley to get alternator hones RPM during idling in D while braked ( lowest idling speed ).

Here is my 200A Valeo between cold and heat soaked when at 550 RPM idle and in D brake hold 550 RPM, poor when heat soaked. At 650 RPM or more all good even when heat soaked.




When I am at a bad traffic jam, and at night ( headlight low beam is ON ), aircond blower only level 3 as highest, brake hold in D 550 RPM, the operation of electric power steering is the power sucker and
will produce deficit where battery has to support the car amperage. Once car move even super slow, as long as RPM is 600 or more all good.

 

Roth wrote :
I cleared the code (which now is only 0705 Selection range sensor defective causing the CEL) & did data logging to see what happens when it returns. Unfortunately I need a Windows machine to print the data & I just have Mac! I will have one soon though. However, I can say the fault 95% of the time has come when I am at constant highway speed for at least a few minutes.

Unfortunately I don't have anything to do load testing with. Anything specific you recommend? I would also like to start doing some back probing of the TCM connector and perhaps the 9g connector at front SAM. Besides this, I think Xentry will do better than me looking for needles in haystacks. I thank you again. Still many of your wiring diagrams to review as well.


Selection range sensor
I believe you can replace that stand alone using aftermarket parts.
If too much metal debris from clutch, this sensor can go banana too.



.
Do be very carerful when removing and re-installing this conductor plate/TCM Y3/8 because there is Neutral/Park and Drive plastic lever ( called by some as MANUAL VALVE ) which can break.


Google it well, many utubes on this thing.


------------


To do load test on a suspected wire, get a 12V bulb a few T10 ones.
T10 , 5 watts version, get 5 of them = 2 amps already.
Or add 1 or 2 of 20 watts version bulb as bigger load.
Resistive load a bulb is , is the best. No electrical noise....but careful it is hot.


I made my own load bank :

0.4 to 7 amps load bank of 2021 : https://mbworld.org/forums/e-class-w...tion-test.html

Up to 77 amps load bank in 2025, to test alternator : https://mbworld.org/forums/e-class-w...completed.html
I have 300+ watts of auxillary lights as load bank too.

I also bought 25 amps ready to use electronic load bank for battery Reserve Minutes test.

 

Roth wrote :
Also forgot to mention in earlier posts (if it's an indicator of a specific course of action), I have relays clicking loudly from the front SAM when I unlock the car from cold. Not 100% of the time, but at least 70-80%. If not relays clicking, it will be an audible electrical click from the battery area itself. Also, if car is off for a few mins and I am under the hood, I hear relays clicking. Not rapidly or excessively, but noticeably. Perhaps the latter is normal? I did swap the horn & circuit 87F (relay R for TCM & Fuel control module) at the beginning of all this & naturally it made no difference.

Some relays will operate when door opened or FOB key pressed LOCK or UNLOCK. These relays are at the front sam box itself.
When car will enter sleep mode, usually up to 6 hours later ( depending on car year and model I suppose ), the final relay you can hear CLICK as in OFF, is the K2 relay in F32 prefuse.
If car been parked more than 6 hours, K2 relay will sleep within 15 minutes of door closed car un-touched and key FOB far away and even when hood is kept open* ( car computer recognize it as workshop mode )


Depending on ignition key switch positions, these are the relays ( the hot ones ) which will operate at all time at Igniton ON - ENGINE OFF






Relays J,K, Q, R and N


Right hand drive car....



The relay which will go kapoot first will be Relay R mini size, small power handling rating and hottest at 47C in less than 30 minutes and engine is COLD and OFF at 30C ambient temp.

 

I am very sorry for my delay in replying. @S-Prihadi, your responses and contributions here are pure gold. I can't thank you enough. I hope tonight I have time to give a proper response and address all the points you have laid out, but for now I at least wanted to give a quick update to one big fix.

The relay "R" being replaced did infact sort out the transmission "Range Selection Sensor Defective" fault 0705 as well as the ECU fault listed in the 1st post on this thread "This error can be ignored and erased". This two faults did/do work in conjunction with each other. I virtually never had actual drivability issues, so it was obvious the Selection Range sensor itself was fine & my transmission has always been serviced every 40k mi. 1st owner had the 1st service done at the dealership (while still under warranty) & I did the other 2. The fluid looked beautiful with virtually no debris or shavings anywhere whatsoever.

I do still have the low voltage bs. I'll elaborate more on my alt, voltage regulator, & LIN unplugged vs plugged in history later, but basically if LIN is plugged in, I am discharging during 50% of driving & while LIN is unplugged voltage is now stable, but loads such as rear defrost, max A/C or the ​​​​largest offender, opening (& specifically) closing the doors makes the voltage drop by 1v or more & RPM's drop significantly. Again, more on this later.

Given all of this, my rear suspension is still a greater concern, or at least equal. It sounds as if I neglect this car, when the reality could not be further from that. I'm ready to move on, but at least one if not hopefully both of these issues need to be resolved so that I can move on to a car where these headaches are actually worth it. Funny enough, the only two areas I didn’t do extensive research on before buying the car were these 2 nightmare areas : the idiotic "smart" (dumb) charging system & the rear suspension architecture that can't even last 100k mi or be serviced like literally every other car on earth.
https://mbworld.org/forums/c-class-w...uspension.html