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Hi All - 2014 E550, 130k miles, without keyless go. I've been having this problem in the winter since December 2020, but have put off repairs because repair men do not know what's wrong and issue goes away when car is warm. Any guidance would be great!
Only when the weather is below 35 degrees Fahrenheit, I will try to start my car with the key but it will not crank. If I continue to try by taking key out and reinsert and turn over many times, it will eventually start. The colder it gets, the more it key turns it takes to start (today it took 5 minutes). I read the CEL codes, and the code I get is "no communication with TCM". I noticed it will only start when the green "E" finally is on (above the PNRD selection, not talking about the ECO, this is fine). Sometimes, the green "E" will turn on for split second and car will crank for split second, but then "E" disappears and stops full crank... This issue does not happen above 35 degrees at all and works no problem - starts perfectly all spring, summer, and fall in NY. When car eventually starts and I drive to destination, car will turn on normally as if no problem - my guess is because car is warm although weather is still less than 35 degrees. After parked for many hours in cold, issue comes back.
Things I've done after having issue:
New Batteries - front, rear, key batteries
Tried both keys (spare and main key)
Replaced leaking engine cam sensors, but was told was not bad and did not leak into ECM (engine computer)
Replaced transmission oil
Work done on car previous to issues (Sept/Oct 2020)
Rough shifting in 4th Gear - Dealer replaced torque converter after waiting 2 weeks for part from Germany, did not fix 4th gear issues... but dealer was generous to give me additional new problem 2nd gear erratic shifting, and power cut out on load
Back to dealer, they think I'm crazy and I keep asking to check and suggest oil level not correct. Transmission was 2 quarts low - they forgot the filler tube on transmission pan for filling.... Dealer apologizes. Power cut out issue resolved, but 4th and 2nd gear issue not resolved.
Back to dealer and dealer claims shifting issue is not there because of driving style and says this is new issue not related to Torque Converter and extended warranty is now expired... after 1 month of bringing car back and forth. I call foul and ask MBUSA to step in. MBUSA, does not help and says too bad.
Should have told he extended warranty, the issue was not fixed. They would pull the amount they paid from the dealership.
More than likely moisture is getting to a connector on the TCM, and is causing the car stop communicating. Does it happen when it rains, or when you take the car thru a car wash that has an under carry sprayer? Also make sure you don't have a leak inside the car.
How handy are you with electrical troubleshooting ?
These are my thoughts....
01. I doubt you have issue with bad cold solder joint at TCM or other module which connects to the TCM.
This is a good news. Bad cold solder will still act up anytime enough heat or vibration happens.
02. Below 35F is as good as zero Celcius or cooler and that zero C is freezing temperature of water.
I am away from my PC back home and has no access to WIS, but reading your information : I read the CEL codes, and the code I get is "no communication with TCM"
That CEL can mean purely lost of communication as in CAN BUS or lost of power to TCM and hence no communication can occur as the com chip is down too.
03. Freezing temperature can cause a wet connector to have layer of ice on its contact male and female terminal, increased resistance may occur.
04. Freezing temperature can cause a weak relay to not be able to engage ( closed circuit ) and I recall 87F circuit is for tranny , based on my M276 3.0 wiring, which would be very similar
to your engine as Mercedes maintain certain electrical standard the same across models. Circuit 87F has a relay or a few relay/s involved.
As an example, go to : https://mbworld.org/forums/e-class-w...-87m-50-a.html
Download the Relay Tree, this one : https://mbworld.org/forums/attachmen...2.065-rhd.xlsx
For my engine and facelift model, Relay R ( at Front SAM fuse box ) feeds power to fuse 33, where fuse 33 is power for Fully integrated transmission control controller unit (Y3/8)
The good news is, Front SAM wiring diagram has no before and after facelift version.
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05. If I were you, I would do below in the order which is easiest for you to do the test first :
AA. RELAYS.
Freeze relay R , J and M to typical freezer section temperature which I believe is -20C for home refrigerator.
You must have proper connector ready and a 5 amps power supply and a test light with at least 2 amps load or 50% of fuse rating in use and a digital voltmeter.
See if your relay/s can engage at -20C and what voltage drop did you get at the 2 amps bulb. Do take into account your power supply voltage drop when loaded at
2 amps plus the load of the relay coil.
BB. CONNECTOR https://www.benzworld.org/threads/li...p0748.3011364/
Wiring harness connector : https://www.ebay.com/itm/234583058174
*This you would need complete wiring diagram if load test is to be conducted wire by wire to the Fully integrated transmission control controller unit (Y3/8)
Unplug TCM side and make sure it is dry, no green oxidation, no oil, no wobbling of the male pin at module side and proper fitment of the female pin and none pushed out of its seating on wire harness side.
The individual load test you can do on a wire , say 2 amps load, and with proper male terminals, there then you can tell if the crimp internally has high resistance or the female terminal springy
bite has now become loose and create bad contact. Its not so fun doing load test on each individual wires, but sometime that is the only way to test intermittent issue you have.
I never messed with the tranny round type terminals. Usually round type terminals are very robust as it uses dimensional accuracy to produce good friction fit.
Unlike flat bladed terminal which its female must use some sort of springy tounge and can get weakened overtime.
The crimping to the female round terminal should be also a suspect as oxidation or bad contact can occur there.
This is how a typical round terminal is crimped :
The connector wiring to the TCM seems very simple. 4 is power (+12V) or circuit 87F and 5 is circuit 31 which in MB speak is negative or ground. 1 and 2 is CAN BUS C.
3 you can ignore. X11/4 is OBD2 connector.
Any circuit 87 in our W212 means there is a relay providing the power, that means it its a switched power source and not constant relay-less on like Circuit 30.
So anytime a relay is involved, it has to be a suspect too as it does wear out overtime from thousands of activations.
Since tranny connector pin 4 is from Circuit 87F and that is from front SAM, lifting up a front SAM module out of its fuse box housing to access its connector is no easy task.
You best jump the terminal 30 and 87 of Relay R to provide the power. If you want to be safe, jumper wire is to have a 5amp fuse.
In German DIN, a relay 85 and 86 pins are always the coil. Pin 30 is power source before contactor point or better known as input.
87 or 87a ( has 87a if 5 pin relay ) is always for the device or power output of the relay. MB does not always connect power source to physical pin 30 of the relay, remember that, it could be at 87.
87 or 30 has no actual difference, but for proper wiring diagram sake 30 is always the power source.
Now you know why i said, if there is a circuit with 87 designation surely a relay is involved as 87 is output of a relay.
See, MB does not indicate which one is 30 or 87 pins of the relay, but a circuit 30 is always a power source and 87 is a 2nd layer downstream power from a circuit 30.
Should have told he extended warranty, the issue was not fixed. They would pull the amount they paid from the dealership.
More than likely moisture is getting to a connector on the TCM, and is causing the car stop communicating. Does it happen when it rains, or when you take the car thru a car wash that has an under carry sprayer? Also make sure you don't have a leak inside the car.
I told MBUSA all that, trust me it's frustrating - especially I was working directly with the shop foreman who was electrically inclined... Unfortunately, I think MBUSA saw how financially pitful the car warranty overall work done on it (air struts, engine mounts, etc etc) thought they [MBUSA] paid enough into the car.
I checked the connector, but will check again and report back. Great idea.
Anyway relay R is low power and not as robust as the bigger one. It is also the hottest on my car
Left small one is relay R for tranny
Unfortunately, I am not electrically inclined, but I can try to learn it without taking too much risk. However, the relay issue was something I initially thought but was thinking these newer relays are not the relays of old. I think its possible as the symptoms in the TSB are representative of my issues. I'll look into it and report back, appreciate the great feedback.
S-Prihadi - UPDATE: I checked the HELLA micro-relays and they were in the defective manufactured range, I switched up the relay with the horn relay (same part number) and it has been starting without any problem in the cold the past two days. I actually feel the starting is quicker. It has been under 35 degrees F (0 Celsius) and it has started instantly. Unfortunately/Fortunately, the weather will warm up in NYC area and will not have confirmed starts in the cold I need it to be to test the problem long term. I am going to do 2 things:
(1) purchase 2 replacement relays with updated part numbers for horn and startup relay (FCP Euro has them)
(2) report back when it becomes cold again for long term study
You still can freeze up the suspected relay and ex-horn one and soon the coming new ones in the freezer for testing sake
True - however, I'm scared that it might permanently break them if I mess around with them. The new ones come in next week, so I'm not taking any chances on touching them as its working...for now...
By the way, I hid the fact that I took the car last year to MB Manhattan NYC. The shop foreman told me I needed a new harness... $10,000+ involving new harness, new cam sensors, new ECM, and many hours of labor in removing the engine out the car, etc, etc.... When I said its too expensive, he said ok I will do it for $8,000 to save the car as its such a nice car... that made it more suspicious. That is when I brought it to another mechanic
(another former MB shop foreman) who then told me I had no oil in the ECM and the leaking cam magnets were not leaking that bad. He cleaned up what he could, but weather warmed and I gave up until I decided to post here. I omitted this because I did not want to sway the conversation one way, just because shop foreman said xyz.
Imagine how much money I would have wasted and problem was a $17 relay on a existing TSB!!! You are a life saver.
Well ....the fact you mentioned freezing temperature caused or one of the parameter of the Tranny No-COM is the dead give away connector and/or relay is the high suspect.
I never experienced car electrical system below zero Celsius as I am in the tropics, but freezing is a mechanical disturbance reality for any moving parts.
Relay has tiny hinge to allow up/down movement of the contact points and that can freeze and stick like how freezer section of our fridge stick stuff together using water moisture which became
ice and ice can be like glue too.
No crank is a condition the car computer/s like ECM will be at if there is no information from tranny as to its operational status...due to No-COM to Tranny.
You can start the engine after a few try is because the moment your ignition key is in position 2 or ready to crank ( dashboard warnings lights up ) the relay R coil is powered electrically and
it gets warm and slowly the warm creeps to the hinge and melt the "ice" or expand the metal enough to free the hinge from sticking.
This is how internally the relay is, but upside down. The contact point #3 and hinge #2 when installed is at the top. The coil #1 is at the bottom.
The smaller a relay is by size and amperage handling, the lower power the coil is in terms of its magnetic pull down force.
Hence being a micro relay, the R relay if not healthy and in freezing temperature would be the one likely to produce mechanical problem first,
instead of those regular higher power relays at the Front SAM fuse box.
Relays are not air tight. I wonder how much moisture can they hold at the internal air-space inside the relay in a winter scenario.
Engine bay ( front SAM ) is heaven for moisture generation because it is hot ambient air and hot ambient air can carry more water moisture or create steam from melting ice.
A rear SAM relays at the trunk won't get exposed to hot ambient air engine bay can produce, its a gentler working environment.
I have similar problems on bilge areas of boats in the tropics.
The bilge bottom will almost always have a bit of water from rain or wave.
So it is crazy humid and wet air in the bilge and in a hot day we can have electrical connectors being "wet" like being in a sauna.
If say suddenly freezing temperature occurs, I bet those wet components will be having thin ice layer where it was wet.
Update - FIXED! I purchased the micro-relays and replaced the two in the front, and the two in the back. I waited for colder temperatures to confirm, and starts normally. Thank you S-Prihadi!
12-25-2022 | 10:15 PM
