Basics Basics Basics? 2010 Mercedes E550 No crank

There are many challenges we face as technicians. Developing a solid diagnostic strategy is just one of them. Dealing with service info challenges to tooling, to the complexity of the systems we work on are just a taste of what makes our jobs challenging.
Watch and listen to an interesting diagnostic dilema Brian Culotta encountered while diagnosing this Mercedes with a No start concern.

[@billyyoder8171]

Thank you Brian and TBT. Good job. Have a blessed and safe week.

[@TrainedbyTechs]

Pleasure is ours Billy. Thank YOU for your support and you do the same. :)

[@larryhurst8958]

My question is how could the customer jump around the problem? With a bad battery, he could jump the car, unless I misunderstood, he could not do that with a new battery so he tows the car? It does seem if the sensing voltage, etc was an issue, would Mercedes not flag code in the rear module? If you had lab scope the input from the rear module would you have been able to see the issue or dropout? Relay click, solenoid click? BTW which relay was correct? Is this just an aberration of a particular car, and control module glitches? Maybe we will start seeing more and more of these weird issues with so many modules doing so much? Great video. And how much do we pay for Mitchell and Alldata monthly, they fail miserably on European wiring.

[@orville58]

I love your videos very good info and in-depth diags

[@TrainedbyTechs]

Thanks Orville58 !

[@brandonsteckler3417]

😆 love the “fishbowl”, that was great! Seriously though, great process, great testing and I love the thought carrying through past the repair: “Why did the Engine ECU fail to drive the relay?” This is a great question and what other techs have to implement in order to remain elite. True understanding of how all the “players in the game” work together to accomplish a task is what it takes to developed sound diagnostic testing techniques on today’s vehicles

[@randygould4109]

have you ever scoped a bad battery with a amp clamp and battery terminals connected to battery and watched the battery voltage fluctuating on solenoid voltage draw it goes up and down . arching the contacts in starter causing high resistance.

[@brandonsteckler3417]

Hi Randy, Can you re-work that? I’m not sure I understand what you are asking, thanks

[@8power0]

THANK YOU FOR YOUR TIME VERY INTERESTING DIAGNOSTIC . I HAVE SEEN ON MANY DIFFERENT MAKES OF CARS STRANGE GLITCHES , THE WORST ONES ARE THE ONES YOU CAN'T DUPLICATE OR NEVER HAPPEN AGAIN . WITH BEING A BIG FAN OF FORMULA ONE RACING AND WITH ALL THE TELEMETRICS ON THOSE CARS IN TESTING OR PRACTICE SESSIONS , I HAVE SEEN EVEN THEY HAVE UNEXPLAINABLE RANDOM SYMPTOMS THAT THEY ONLY CHANGE A PART BUT NOT EXPLAIN OR PINPOINT WAY THERE WAS THE ANOMALY . SO I WOULD SAY WE STILL HAVE A LONG WAY TO GO WITH EITHER MORE DATA , TESTING TECHNIQUES AND COMPLETE INFORMATION .

[@TrainedbyTechs]

Thanks for watching 8Power :) It's exciting to see how vehicles evolve over time.

[@ryancolley7608]

A very good video Brian, with regards to the no control, its always hard to determine the cause, however as previously stated if there is a style of open circuit/short circuit sensing then almost always i would expect a dtc to be set by the ecu that is seeing the problem. The feed through the fuses i would say is unlikely to be a sensed circuit as it will only ever have 12v on that side of the circuit whether the circuit is open or the relay is closed. But it is possible for anyone of the modules to drop there feeds via information on the CAN Bus if they are not happy as you said. it would have been nice to see what was missing from the relay, whether it was the 12v feed the ground or both! that may have answerd a few questions. however i know that they (Mercedes) have a logic built in that when the start button is pressed the DME (ECM) looks for a rpm signal to confirm the correct operation of the circuit and if the time elapsis with no RPM increase it will switch the circuit off! if you take a look back at the original diagram of the relays, the DME produces both the ground and 12v feed to the relay however the 12v feed also branches back into the ECM. this is the confirmation feed back into the ECM that tells it that the feed has correctly been deployed by the ECM to the start Relay. ( a sensing circuit)

[@brandonsteckler3417]

Thank you, Ryan

[@PaulysAuto]

This is excellent information and answered the question in a way that makes complete sense....Thanks for this!

[@VoltageDropDiagnostics]

Good video fellas! Im really surprised that a 7.5a fuse is feeding the starter solenoid. Seems low, doesn't it? Did you happen to compare the OEM wiring diagram?

[@Houstontex23]

I'm watching this video while waiting for AAA. I'm having similar issue with mine. I did try to jump start it, but I obviously knew the battery is not the problem. It's brand new. It did have long cranks at times, but mainly Sundays when I'm turning and off the car multiple times during the day. Immobilizer is fine I can only guess for it to be the started or the crankshaft position sensor. It has no codes.

[@JuanOrtiz-mo8be]

You are 100% right the Sam module can shut the signal to the starter you would get a code were too many cranking attempts had fail . Since the Battery was disconnect , memory was erase . I would have put amp clamp around the feed cable of the starter to test the load. Thanks for sharing its frustrating with this computer on wheels .

[@zfloz9895]

You would not get any current flow, as because the relay was not even commended, right?

[@mikechiodetti6737]

I've never worked on European vehicles, but there's more to this puzzle than Domestic or Asian. Did you try to jumper the starter solenoid with 12 volts to test the starter? Or jumper the starter relay load side to see if the starter operated? Those two tests are quick. If the starter did work, then comes the control side. If the starter didn't work, fix that problem then test the control side. Don't know about that sensing a problem in the starter control circuit in the rear module. Shouldn't there be a code for that if the module can do that?

[@brandonsteckler3417]

Yes, this is what Brian is attempting to learn. How Nodes network to accomplish a goal is ever-changing in our industry. It can/will vary from Vehicle to vehicle. Trying to stay ahead of “what’s possible” Is in Aall of our best-interests.

[@TrainedbyTechs]

I hadn't checked to see if the starter would crank from the relay until AFTER I had relay control restored. The first test I did was at the S Terminal at the starter because it was easy to get to and the end of the road. I didnt have control at the end of the road so I went backwards to see why. If control was present at the starter, of course this diag just became real easy. Basic right?

[@mikechiodetti6737]

@@TrainedbyTechs I believe I understand what you were testing and thinking about the module "sensing" the non operating starter, however, that could have been a bad wire terminal at the solenoid. What I was saying is apply 12 volts to the solenoid terminal, be it a threaded screw or a flat terminal, NOT the wire terminal from the relay. To be sure the power cables from the battery are good, connect a meter to the solenoid bat term and starter case. Apply 12 volts to the solenoid terminal. If it turns the engine over, monitor the voltmeter. Any questions regarding voltage drops, bad battery, poor grounds will show themselves. Then the control side should be tested. Sound like a lot? Wait till you have a 3 axle truck with a Cummins or Detroit or International or Mercedes DIESEL in the engine bay! The truck "may have" 2 or 3 group 31S(Stud) or 31P(Post) batteries in parallel. The "Cranking Motor" has an "External" (Ford Type) starter relay to activate the cranking motor solenoid. With all that and more, it's still "Basics," just more of it, but you must be thorough!

[@malibuStroker]

I usually start with a relay jumper to separate the load circuit from the control circuit and test the entire load circuit. I am also curious if it was disabling the starter, would it not have a data pid for that? Great video!

[@rquintero2684]

Awesome, thank you for sharing that

[@richardcranium5839]

heres a thought- that starter has a pull in and hold in winding in the sollenoid. the hold in is usually hooked to the battery via the contact disc when engaged but also within the sollenoid as a common ground. therefore yes it may be possible it sensed the fault. but what type of fault detection would it have? there would be no sense in an open protection since there is no flow. and over current protection should have at least blinked the light. one thing i learned years ago on starter problems- test and confirm the battery is good. then use jumper cables and a clamp on ammeter and confirm the starter is good. bypass everything in the vehicle by doing this. then continue on as needed.found way too many that if they did work they were drawing too many amps and were on the short list for replacement anyway. that extra strain is hard on other components. or was the rear sam dropping out??? you may get a second chance on this later.

[@fascistpedant758]

I wouldn't trust a diagram showing a 7.5A fuse feeding a 20A fuse for a starter solenoid.

[@xaviergonzalez5145]

I think the same! No sense!

[@brandonsteckler3417]

I don’t believe he does trust it. But it is the diagram he has available to him.

[@tinkerwest]

That is truly odd...most likely inverted in [rint.

[@GregoryBirulkin]

How much amperage does your headlight circuit checker draw? Relay signal to energize the coil should be low amperage. Circuit protection is usually done by a current limiter/circuit continuity through internal module circuitry to To the starter relay signal circuit. Which generates a code.

[@TrainedbyTechs]

I used a conventional incandescent bulb test light across the relay control. The headlight was used on the S terminal going to the starter. That circuit certainly is capable of more ampersge than a headlight provides.

[@Gmansour1971]

One time I was at a friend's garage. He had a customer come in that day with a station wagon complaining of an interior beep heard every 20 or 25 seconds. I told him a story about a lady in a BMW X5 that I worked on years before. She came to have a repeated 20 second beep checked out which was coming from the interior of her truck. After checking under the cargo floor in the rear I found an old Smoke alarm that had a weak battery causing the beep. How did I fix it? I replaced the battery, of course. Well, you would never guess on the wagon that came in that day what the problem turned out to be. A smoke alarm in the trunk, in a milk crate, under a blanket, with a weak battery. Freaking nuts but I love it.

[@naushadali95]

Great video.thanks

[@larstottonful]

Around 8:41 you are trying to locate the starter relay. The second picture isn’t identifying the relay, it’s identifying .the front Sam. N10/1 is what MB calls the front Sam. The relay would be N10/1km. So the picture is not wrong.

[@kdautomotive1165]

Had a S class a few weeks ago. Trying to find out what inputs needed for start enable is a nightmare. It ended up being the starter lockout contact in the trans that was a fault. No codes and no SI sucks.

[@TrainedbyTechs]

I agree! As noted, service information for those types of things is very difficult or impossible to find in my experience.

[@kdautomotive1165]

@@TrainedbyTechs I have a question. At what point do you request to bill for more time

[@TrainedbyTechs]

@@kdautomotive1165 when there wasn't control to the starter the diag went from a standard .5 to 2.0 hrs billed

[@kdautomotive1165]

@@TrainedbyTechs after I had a hour in we asked for more time and ended up at 2.5

[@billyyoder8171]

Modules that control outputs and senses (measures) no, low, or high current flow will set a DTC. Issue concerning starter relay identification. Place yourself and tooling in a safe location, then remove relay and jumper switch terminals. Or, touch relays while someone turns key for you. Or, use scan tool output control of starter relay, if available. Control test would only work if starter relay, control circuits, and modules are in proper working order.

[@eastmanautorepair5130]

Good video with good end this is happening when stater relay is stick if hit little on stater relay it will work

[@jesusaucar4178]

The resistance in the brushes is fluctuating, and it dropped low enough to create a signal to the relay, but obviously not low enough to spin starter.

[@jesusaucar4178]

This is why the headlight lit up, but starter wouldnt spin. great video! keep them going, thank you!

[@georgebonney90]

Good question and video, thank u

[@TrainedbyTechs]

Thanks George

[@CubasAutomotive]

Great video!! Such a "typically" easy circuit and to go for a ride is such a frustrating experience for sure. The only thing I would've done differently, especially when having conflicting info for the starter relays, was to power up those relays. I have the AESwave uActivate tool, but many times looking at the relay, you can tell which is the load. I truly expected you to do that when you hit that point in the diag. Would that have cut things shorter? IDK. You might've still had the issue of seeing the control side not working. It's quite possible you wouldn't have sold the starter until you verified the entire problem with the vehicle. As they say, hindsight is 20/20. I've learned so much just fom our chats behind the scenes, Obviously, I'm not the TBT group, but I'm in various others with DeFazio and many other YTers... or groups with some EXCELLENT technicians. It's amazing what the networking can do!! Looking forward to reading some answers! Thanks so much Brian, and the other members of TBT!!

[@TrainedbyTechs]

I did not attempt to activate from the relay because I already previously proved I was missing trigger voltage on the S terminal at the starter. I immediately went to see if I had control to the relay and it was missing. I definitely wasnt thinking a relay bypass tool would do tell me anything because I knew the control was missing at that time

[@CubasAutomotive]

@@TrainedbyTechs I completely understand that. For me, the only reason I would've activated is to know for sure which relay & circuit I was dealing with, just in case of having to do circuit integrity tests. Not to prove if starter worked.... because up to that point I wouldn't have suspected it to be an issue. Now would we have gone a different route when neither relay circuit engaged the starter? I may have used a test light to see circuit activate, and the other circuit would've activated a fan or some other component which hopefully would've been visual or audible. Again, for future testing... in case I had to chase wire issue for control to fuse box.

[@mikem1014]

wonder if the rear module has pid that gives you this info .. an why no fault codes

[@V10PDTDI]

Good to know I know on a BMW It will trigger a fault code I was watching this video and I was thinking to myself ok now you found hopefully the right relay for the starter I personally would’ve put 12 volt on the side of the relay that supply power to the starter solenoid to see if the starter would actually turn the motor then I would’ve proceeded to try to find why the relay wasn’t being triggered it’s probably easy for me to say now I guess.

[@adamapsitis6325]

Would be interesting to see if fuse 5 was pulled, does 7 remain hot? I wonder if the supply is really coming from the rear SAM module or is this a switched input for the rear SAM to confirm relay activation upon crank request? Most of the protected circuits I've dealt with aren't fused as they have over current protection. Also a protected circuit would usually have enough logic to set a DTC eg short, open etc. Great video though, when it doesn't make sense, revist your test steps, think what you can do differently.

[@oldsilkhat7893]

I would assume the SAM communicates with the ECU. So if the start process was initiated but there was no CPS signal, my thought is the SAM logic shut it down. Just my 2cents

[@jesusaucar4178]

Its simple! the sam module is seeing a crank request, and it isnt seeing current flow, or voltage drop on the s terminal, so it knows there is an open, or discrepency on that circuit, so to protect the system, it just says, im shut down until I see some activity on this circuit, wich is probably open, due to brush contact on armature, or a solenoid problem where it isnt completing the circuit, and there may be some bias voltage involved for diagnostics on this line as well.

[@85jmccoy]

It's not simple when you can't find that information if that's is in fact true.

[@joachimjohan1215]

did u unplug the relay when testing? maybe the computer needs to sense the + through the relay coil?

[@SuperMarioDiagnostics]

That was too funny 😂 Great video Brian. One question, when you mentioned doing a voltage drop test to the B+ at the starter, what load did you place on the circuit? I find it difficult at times to properly load that circuit in the case of a inoperative starter. Thanks buddy As for the rear Sam circuit fault detection. I could be wrong but I'd assume that it would throw a code in the case of a fault. As for why you didn't have control, that's a good question.

[@TrainedbyTechs]

I used my headlighlt on the large starter cable while commanding the starter solenoid with a power probe. This isnt exactly a true voltage drop however I know the voltage potential didnt fall on its face when commanding the starter which proves that isnt the problem

[@BTCAutomotiveTech]

@@TrainedbyTechs Just to confirm, the large starter cable was still connected to the starter when you energized the solenoid via Power Probe? If so, that was a valid test. I would also be surprised if there was not a DTC if the SAM was in a circuit protection mode.

[@TrainedbyTechs]

Yeah unfortunately there were no codes in any module when the vehicle arrived to my shop. There could have been prior to the customer replacing the battery

[@TrainedbyTechs]

And yes. The big battery cable was still attached. I placed my headlight on the large post on the starter and actuated the solenoid S terminal. If there was a voltage drop causing a no start, my headlight would go dim

[@picoboo5048]

I use a battery load tester to test when starter is inop. The toaster style tester that is. Could also use a carbon pile tester

[@zfloz9895]

After I remove a light bulb of interior lighting from a dor panel, în a Renault Laguna, I place it back and it wouldn't light, as I was measuring the connections, they hade 12v , but still the light bulb did not turned on. I replaced the bulb and still nothing. After a few ignition cycles, with the bulb in place, the confort module re started the light bulb again. I connect the scan tool , and was a pending code about it . P.s. the 12v that I was measuring , was a low current ceck procedure sent by the confort module, to re measure the circuit resistance. My folt was that after I pit back the bulb I did not cycle the key (witch was keyless entry, and keyless go system ). :)

[@fsteddie98]

How did it go from what sounded like a battery draw(New Battery/Having to jump) to a bad starter? Do you think it may still have a battery draw why and why not?

[@GregoryBirulkin]

You should have put a picture of Keith in the fishbowl. 🐟🚣‍♂️🦈🎣

[@keithdefazio9613]

🤣

[@JOHNPHUFNAGEL]

Is it possible that you just didn't have a good ground or connection on your test light? I have chased my tail a couple times on similar tests by a little paint or corrosion on the terminal. Great case study

[@TrainedbyTechs]

Trust me I verified nine ways to sunday if I had connection issues when the problem arised. I too have been burned by self inflicted wounds many times :)

[@PaulyD0859]

I can’t get over the irony of the fishbowl in the trunk! It’s about time Mercedes finally made that standard equipment. As a flat rate tech, the lack of service info and the inaccuracy of the little bit of info available on these cars makes my guts churn every time I get one. Having to “wing it” nearly every single time is sooo tiresome. I’m not a volunteer and losing my butt on these POS excuses for “high end” automobiles makes me wish my shop would tell people who own them to GTFO!

[@CubasAutomotive]

100% agree with your ENTIRE comment! lol

[@franciscovera828]

I agree also,fuck them junk cars!!!!!

[@Peter-hc4di]

@@elwjlw hahaha....

[@fivefortyeye540ia4]

What you expireced is called "current limiting technology" Simply put, a control module has the ability to turn a circuit off momentarily incase of a short, or in your particular situation High resistance. Be

[@JOHNPHUFNAGEL]

Why would it shut it down for a open or high resistance? With either one of those the SAM module is in no danger of getting damaged unlike a short or high currant

[@fuckjewtube69]

@@JOHNPHUFNAGEL And also why wouldn't it throw a code? It absolutely would throw a code for this.

[@2secondslater]

I'm looking at that 7.5A Fuse No.5 feeding that 20A Fuse No.7 in the fuse block/power distribution module and thinking there is something internal in that block ie. a transistor or some other control or power source that is not shown in the aftermarket diagram, that could have a fault such as a bad solder joint and possibly that the cranking attempts have temporarily welded the joint, just a thought.

[@2secondslater]

Basically you could have an intermittently faulty fuse block/power distribution module

[@2secondslater]

Power checks at both Fuse No.5 and Fuse No.7 when the vehicle was faulting would probably confirm this.

[@2secondslater]

I mean, why else would a 7.5A fuse feed a 20A fuse?

[@2secondslater]

The 7.5A fuse to protect the SAM from excess current and an internal relay or what have you in the fuse block which provides higher current to the starter solenoid which draws above 7.5A but below 20A?

[@blehem]

I'm years late to the party, but have some thoughts as a former CDT for Mercedes Benz. I'd love to talk about this if you are still interested in what may have happened.

[@christortora2967]

I'm almost a year late to the party you started - I want to hear what you say

[@nicknicu1787]

In the beginning of the video you’ve stated that you have a power and a ground coming into the starter relay. You’ve determined that the ECM is not grounding the relay. However you didn’t mention whether you’ve checked the power coming from the ECM into the starter relay? Also a Main power into the relay was coming from the rear SAM. Did you have that power present when the car wasn’t cranking? Is that a key on power? I assume that the rear SAM has to be energized in order to send power out to the starter relay... First of all it’s really frustrating because the service info was lying to you! You can’t diagnose a car properly when you have to guess which one is the starter relay and how it’s controlled,you just have to know! Good video! 👍

[@TrainedbyTechs]

In the beginning I was explaining the circuit. When it came to testing at the relay, B+ was available from the rear sam. And B+ was available from the ECM. I was missing ECM ground control. Sorry for the confusion

[@nicknicu1787]

Trained by Techs Thanks. If I had to guess...and this is a pure guess : I’d say that there’s a “ sensing “ wire somewhere and that the wiring diagram is simply lying to you...especially since this is a Mercedes-Benz and aftermarket wiring diagrams are not too good. I’d also say you will have codes except that in this case,the battery was disconnected. There’s no way that a Mercedes-Benz doesn’t throw some “ Battery too low or Low voltage codes “!

[@parochial2356]

Everybody is a Monday morning diagnostics expert [as in me :] but here is my take of all of this. I am a little confused by the path and direction taken in this video. First, we are told it was a "no start", then we confirm that it was a "no crank". Everyone here knows the difference between the two. A different approach/direction is taken with each. It was subsequently stated that the actual problem was a "no crank" situation. [Service writers take note and save your techs time through through interrogation of the customer before assigning the vehicle to a tech.] In my way of thinking, I would have started by making sure the battery was at least 12.6 volts. After figuring out its location [ :) ], I would have put a relay tester break out block in to fuse box and reinstalled the relay. A minute or two with a test light or DMM would have shown either no control to the relay or no power out to the starter. In this case there is no output to the starter from the relay. I would then jumper the relay output. If the starter cranks the vehicle, then the relay is either not energizing with control or there is no relay control. I would proceed to check for a bad relay or troublshoot relay control. A quick relay swap [if possible], resulting in successful cranking, on top of what I saw when testing the relay [control input] with the break out block would have 100% confirmed a bad relay. Otherwise, I would have had direction that the problem lay in the "Drive Authorization" system and diagnosis of that aspect of the system was my next step. For whatever reason, this tech was into the "Drive Authorization" path when ultimately the defective component was the starter itself. Perhaps not doing as I say versus using a low amp load headlight [versus full field draw by relay bypass]threw him off ? Perhaps the SAM saw a 3-4 amp headlight load as OK, but the full field load current was excessive [shorted] ? Again, jumpering the relay, or bypassing the relay would have produced a no crank and pointed to a starter or wiring issue between the relay and starter field or a starter grounding issue [?]. One commentator pointed out that the customer would apparently jump start the vehicle when it would not crank. This does not seem to add up when the starter was ultimately the issue. Question the customers more thoroughly as to symptoms and any remedies or work arounds tried before assigning the vehicle to a tech.

[@downtowntodd767]

Just playing devils advocate here, perhaps a bad connection while doing the original test with the headlight led you astray. I can't imagine that a module would keep a secret and not brag about keeping the car from starting. As you pointed out the MBs love to set codes in multiple modules. You would think something as fundamental as the starter circuit failure would cause codes in at least 9 modules.

[@TrainedbyTechs]

I would think the same as well. Unfortunately there were no trouble codes in ANY module. And also, I confirmed my connections multiple times. This is a habbit i've learned over the years by being BURNT by my own self inflicted wounds

[@ntblb89]

We like to see videos as practicall diagnosics . Not only talking .

[@RR-bt5xv]

what about the battery problem?

[@TrainedbyTechs]

The battery was replaced by the customer. I did confirm there was not a parasitic drain and also that the vehicle was charging after the starter was replaced. I believe the battery was original prior to the customer replacing it.

[@burtpilon1735]

Maybe some how it senses ghost voltage somewhere ? Just a guess. Lol on the fish bowl

[@eoinhenderson1819]

I see this now many times on Newer European cars , no control to activate component , But it is a Component Fault!

[@joekeefe3229]

rpm signal?

[@TrainedbyTechs]

Can you elaborate on your question Joe?

[@joekeefe3229]

Just thinking what could disable a starter, rpm signal missing or battery current sensor going high on crank

[@TrainedbyTechs]

@@joekeefe3229 The vehicle wouldnt even "click" when it arrived. There certainly wasn't and RPM signal as it didn't even attempt to crank over. It's possible there could have been a high-current situation BEFORE I got to the vehicle but one would assume there would be trouble codes to follow that strategy.

[@joekeefe3229]

@@TrainedbyTechs yes i forgot about lack of trouble codes, I had a Chrysler sebring interm starter solenoid fuse blows, service info gives ohm spec for the solenoid, starter would work crank sometimes, when it worked all was good. when the motor wouldnt crank it would blow the fuse. buy a new starter, I ohm the solenoid, it ohms low, crap, bad new starter? I put it in anyway to see how it goes. I put a amp clamp on the solenoid wire , crank the car its fine , draws about half the current of fuse. then I thought oh ya when the car cranks theres voltage drop and lower current to everything. When it no cranks current to the solenoid would go up and blow the fuse with the old starter. Idk, just thinking about car and why benz would do what they do. True there should be a trouble code.

[@darrenogorman121]

My personal takeaway, Test without disturbing circuit.

[@fascistpedant758]

This whole story sounds fishy to me.