The MYSTERY Mercedes - Part 2 (Thanksgiving Special)

[@paulsullivan6392]

It might be prudent in order to save a "new" computer to repair/replace the faulty wiring harness THEN try the old computer and or the "new" computer. Regardless...your dogged determination on this diag is nothing short of outstanding. I hope you are with family and friends today and that you have a Blessed and Happy thanksgiving.

[@PineHollowAutoDiagnostics]

Thanks Paul! Yup that's the plan! Stay tuned for Part 3 😁

[@michaelcoachtechvp2846]

No repairing that harness lol you would never repair all the problems chasing your tail replace engine harness

[@sweetwilliam49]

@@michaelcoachtechvp2846 I don’t know, Ivan is pretty good

[@michaelcoachtechvp2846]

@@sweetwilliam49 nothing much left to repair the whole harness is biodegradable its made of peanuts. It was a common problem on MBs of this era need a new engine harness

[@WCSPete1]

I was also worried he'd fry a good computer before fixing the harness. Worry over thank God. Also in part one, it was mentioned a change of CKP for something similar. What happened to the original CKP? Or does the scope pattern role out the need for concern here?

[@jonalowe]

Common issue on most Mercedes from around 1992 till around 1996. Biodegradable wiring. Need a new Delphi engine harness. Some cars require multiple harnesses replaced. Probably find a good upgraded used one on eBay.

[@ebutuoyebutouy]

Yup! A number of folks mentioned this in part 1. I know, I'm the proud owner of a 94 s124. Lol

[@jonleyton7905]

Biodegradable harness! Love it, replaced the engine harness on mine, fixed it.

[@mikefoehr235]

German cars are bio hazards.....stay away.....far far far away

[@2nickles647]

I fixed my own harness. I had wires of the same length in my stash. Rebuilt my harness on my 2000 Discovery 2. No need to order a harness. She has been puring for many miles now. Going on 2 yrs.

[@johnshellenberg1383]

I can't believe this car has the original harness, not many do now, they all rotted away years ago. But, yeah, it needs a whole new engine bay harness and hopefully the engine computer isn't fried too, which often happened. W124 were awesome cars until 1992/3. The 24V 3.2 engines have shit head gaskets and the wiring harnesses are crap. The previous 3.0L 12V cars were bulletproof wonders. After about 1996, MB took a huge nosedive. We bought a W210 E-Class and a W202 C-Class and they were just disposable garbage cars. They sent us packing to the Toyota dealer and now I'm still daily driving my 2004 Highlander with 400K on the clock and she's still a strong reliable runner.

[@BDKennels]

That was so far beyond my skill level I feel like a kindergartener. Color me impressed Ivan. It's your "This car ain't beating me" attitude I most admire. You always find a way.

[@bobbydelamar606]

This is like watching a TV show. I can't wait for the next episode.

[@kdmq]

I definitely think something related to the coils is fried inside the computer because, if you remember, there was a code 47 at the very beginning of the diagnosis. Go to 19:54 in part 1 I found that code 47 is "control of ignition coil preloading voltage exceeds limits" but it never reset that code after you cleared the fault codes. So I definitely think something got cooked inside the ECM that is causing it not to even be able to set code 47 anymore. Seeing as how the computer is still _capable_ of setting code 24, I am going to speculate that the CKP issue is a totally separate issue (probably built in by the owner when he fired the parts cannon). Whether the car is gonna run or not with just a new ECM therefore is anybody's guess.

[@pantherplatform]

Wasn't that after replacing the battery tho?

[@kevinbyrne4538]

I really admire your patient, persistent, and methodical approach to solving these problems. Other people might find it boring or plodding, but it's the only way to expose these bizarre problems.

[@PineHollowAutoDiagnostics]

Thanks Kevin! I save the really good ones for the holiday specials :))

[@drjohn5801]

Agree - replacing the ECM without repairing/replacing the harness is courting disaster = damage the second ECM.. mighty sporty man. But, DO love your TS methodology and dogged determination - I have a colleague whose motto is: “The difference between success and failure is never giving up.” I see this in your approach - well done! 🙂

[@laszlototh5956]

I think you are right about the cooked ECU. But I would not connect a working ecu on a known bad harness. Amps are quick, they can kill an other set of drivers in a blink of an eye.

[@PineHollowAutoDiagnostics]

Yup definitely don't want to fry the replacement ECM!

[@sir_frag1868]

Your diag skills are nothing short of amazing. Also your diag skills when learning on the fly like this just takes it to whole new level of greatness. I never let anyone touch my cars. EVER!!! If I did ever get stumped on anything, I'd definitely let you give it a go. I'm from CT too. I'll make the appointment and flatbed my ride in person just so I could learn something new. I'd gladly pay the extra customer annoyance fee lol

[@sheeshalready]

I owned two of the 1990 300TE wagons just like this one. The bullet-proof you speak of ended in 1992, I believe. The rest of the 90's were plagued by wire harness fail issues, exactly like you are seeing with this car. My older W124 never had wiring issues, just the usual mechanical stuff over time. Great series, Ivan!!!

[@timbo19751975]

Crumbley engine harnesses are common on these cars. They are commonly replaced over here in UK. Replace the harness first, before plugging in a new PCM !

[@joecoyne5660]

My son had a 93 Mercedes with crumbling wire insulation problems also, his were down at the starter, he chose the best long term fix and sold the car to someone ready to take on continuing wiring problems.

[@jimmacris615]

Had a very similar problem on a 97 E320. The spark plus shielding around the coil basically rotted away die to age. Could not find a suitable replacement part so I Got hold of a junkyard MY and ended up pulling the whole wiring harness. Worked great.

[@aldrinalmario1513]

Typical for this W124 model to have failing wiring harness insulation as I mentioned earlier Ivan. I believe you need to suggest to the owner to have a complete new wiring harness installed as fixing just the harness leading to the coil packs alone may solve the initial problem, but quite sure that other subsequent problems will arise until the whole wiring integrity is corrected. If the connectors are still alright, a rewiring job can be done, but if most of the connectors are starting to deteriorate, then a new harness with new connectors may be the best option to go. Looking forward to your plan of attack to fix the issue and good luck! Cheers!

[@compu85]

On a car with electronic throttle I’d def want to do a full rewire. Just too much risk to fix half of it.

[@brandtharen]

This has been a very interesting investigation so far. But I can't believe you haven't defeated that door buzzer yet!

[@fredboomboom5503]

In my previous life as a parts guru I sold plenty of 960 Volvo ignition coil connector kits they would go bad and needs to be replaced all six just remembered love you Ivan God bless take care

[@andrewmarkland9411]

Possessed Merc. Crusty harness. Blown computer. What's not to like! Great stuff this Ivan...

[@peters1821]

Great video as always! Mercedes had problems with the harness early-late 90s especially on the w140 (S class) models. These e320 s were really good and reliable cars. 95 is the last year they made it! New ecu and harness repair should keep this car on the road for many more miles!

[@arthurfricchione8119]

Ivan Happy Thanksgiving. Let’s see what happens in pt.3. 👍

[@powayimports4175]

This era had known wiring loom failures. We used to replace the complete harness as it will short in multiple places.

[@alexg9155]

So my guess was right, code 47 was something about ignition coil voltage exceeding limits, which makes sense as 12V on the signal wire should not be happening. ECM is probably toast though. Then the owner threw the wrong CKP at it trying to fix this problem, hence it's a separate issue, I think. We'll see. Fantastic diagnosis as usual!

[@alrifainidal]

well done Mate. yesterday I ran to the same issue but it was kia Cerato no spark for all the coils

[@CXensation]

You defo need new coil wire harness. Watching you opening up the ECM seems to me it is very easy to replace the drive transistors. They would probably be a fraction of a new junkyard ECM. In previous videos you have demonstrated good soldering practice. Worth a try ! As always you have some special cases in your videos, very interesting ! Thanks for the effort making and editing these videos !

[@MrPitatom]

I've been told that Merc wiring looms from this period are bad. It's unfortunate because these Mercs are great cars. As always, excellent diagnosis Ivan.

[@cullenmiller8170]

I would open up the harness first before I would plug in the next ECM. Sometimes you can go back several inches and the insulation is in tact. Than you just have to get the wire stretcher. A lot of the pins in the connectors are soldered and can be reused.

[@AdelJeffreyJeffreysAuto]

At 95 they switched the wiring protective plastic to organic biodegradable type thats crumbles away with time causing myriads of electrical problems! Known issues on the 95 onwards w124 . I remember that i read it somewhere on w124 forum.

[@steveo6631]

Hey Ivan, you get the craziest cases... It must be so satisfying to reconcile these wacky problems after seemingly no one else can... Based on this video and data from part 1, I'd put money on having a bad ecm ignition driver... I always enjoy your holiday specials.... Peace...

[@_RiseAgainst]

In most of his cases the car has stumped multiple mechanics before it gets to him. In those mechanic's defense, diagnosing obscure problems doesn't pay well and pisses off the shop managers.

[@Ulrich_Wolf]

As recollection serves, this era of Mercedes had a biodegradable wiring harness insulation material. Meaning that my bet is that the ENTIRE engine harness is just as much shit as those sections you see at the coils. Replacing the engine harness will ensure that you don't blow another PCM sky high!

[@lxfguits]

Just a tip. The hood has a service position and can be lifted straight up. Makes it easier to work in the engine bay. Most if not all mercedes cars have this feature.

[@adotintheshark4848]

When they changed to OBD2 starting in '96, it was a blessing because all the manufacturers had to standardize their emissions and engine controls. Before that, with OBD1, you were always on your own depending on which manufacturer. And Mercedes was not kind to wiring harnesses in the early to mid 90s. Their insulation was soy-based, and if the mice didn't eat it , it would deteriorate anyway.

[@akdenyer]

Hi Ivan you could look up the power pass devices and if transistors check for correct resistance EBC should indicate diode operation. You could resistively load the output pins with say 100 ohms and check to see if still switching. Early driver circuit probably with no current fold back to protect itself.

[@hightttech]

I want to see him dive into testing the drive components as well. He is electronics enthusiast; I bet he cannot resist.

[@Graham_Wideman]

@@hightttech ... well he can't resist while wearing shorts anyway!

[@dans_Learning_Curve]

Interesting rust/corrosion on various parts under the hood. Makes me wonder if this car was flooded st some point. Great job getting from not knowing anything about this car to getting where you are now!

[@pinecone01]

Looks like the Thanksgiving dinner is all here! Turkey, stuffing, Ivan, an overly complicated German car, cranberry sauce... etc. Love it, man!

[@PineHollowAutoDiagnostics]

Enjoy!

[@zoidberg444]

You forgot the Borscht comrade!

[@KarateSensei71]

I was expecting rodent damage not degraded insulation. If you fix the obvious shorts, I think you have a 95% chance of it coming back to life (fingers crossed). With you the job I know it will run again flawlessly (eventually). Happy Thanksgiving to you Ivan and to all of your grateful fans around the world.

[@RichardHeadGaming]

I would fix the harness and retest before getting a PCM personally then if needed a PCM, but the CKP sensor code may or may not be related to the coil issue (probably not). voltage is gonna return on the secondary wire to PCM from the coil in order for the PCM to collapse the field. So shorting the two leads might not have any bearing on PCM health just won't let it fire the coil. could easily unpin the coil wire feeds from PCM and run a jumper set to a coil to test fire them.

[@gwick358]

Thanks for these holiday specials Ivan. Always informative and entertaining. I hope you keep finding stuff to show us. Happy Thanksgiving to you and your family.

[@MrKinyodude]

Fix the harness short, plug new ECM ... hope for the best. The old ECM probably busted its transistor open due to the short, and if so, can be repaired.

[@averyalexander2303]

Very interesting as always! As crappy as that insulation looked, I question whether that car will run reliably even with new wiring to the coils. I can't imagine the rest of the wiring looks much better. Common problem on those cars. What a shame, I bet a lot of those cars got scrapped because of bad wiring.

[@MacCaughey]

Yep, I lost one of mine that way. I traced an uneven idle to the MAF wiring. I fiddled with the wiring with the engine running and the loom suddenly went up in smoke. I was just too slow getting things disconnected and the damage was severe. The car was structurally and mechanically sound, but the wiring looms were just too expensive to replace and it had to be scrapped :-(

[@shaneharrison4775]

A new ecm is a must but only after wiring has been gone through and repaired if all coil power feeds are toast as well as sensor feeds then they should all be rectified befor tossing a new ecm in the mix perhaps a bit of tinkering on the old ecm could help in clarifying the toasted issues

[@geepeerces]

yup, the dreaded bidegradable ecojunk harness on 93-87 MBZ's. On these 3.2L, you need to replace the whole top harness with an updated one, AND the throttle body (which has cruise control and idle control servos in it with a captive cable). the lower harness is probably bad too, I noted you saw no oil pressure when cranking.

[@andygirke846]

Thank You , Ivan, for the Thanksgiving Day post, Happy Day to you and yours my Friend. 😎🙏✌

[@roxanneabbott8424]

I'm with Paul Sullivan on this. I think better to fix harness 1st then try with ECM! Another awesome study!!

[@Pitmanworker]

As it is evident - fantastische maschinen das auto ist. :( Oh.... I was hoping this time it will go away from the embarasing moment, when you discover that the german engineers put together quality machine indeed, but just at the last moment decided that a compromise with the cables insulation (in the name of a marketing purposes) is not a biggy. Exceptionally well done Ivan! I don't know how many of these Mercedeses you worked on before, but around here they are infamous with the problem you found on the wiring harness. Many of the people commenting on the first part video were correct. When you see W124 or W202 model made in the mid 90s the first thing you check is if the whole wire loom in the engine bay was replaced. If it happens not to be (as you see) you start to realize that this car is no go from now on. You are quite lucky having access to another known good ECU. Usually these parts are in the unobtainium category. It is quite remarkable though that the HFM-SFI modules could be disassembled, the PMS ones made by Bosch during the same time are sealed like they should withstand nuclear strike. It is even more interesting that they (I reckon this module is made by Siemens) use descrete components with not erased identifications. In the Bosch PMS the components are made using CoB (Chip-On-Board) technology (imagine late 80s CoB - again way ahead of time) - you can literally see the crystals of the transistors and the ICs and the gold wires going out from them to the PCB tracks. No packaging, no insulation - the whole board is submerged in something like transparent slicone based solution - frozen in time. I still think though that may be this "blown" ECU might be salvageable. It would be interesting what are those transistors (Bi-Polar or MOSFET) according to their inscriptions. Did you have the chance to check that they indeed are blown off? You said it must be a chip level problem, but keep in mind this is technology from the 80s (when W202 model was conceived - from where this managment system is borrowed to the latest W124) most likely all those "big" chips on the board are either CPLD, FPGA or ASIC . No CPUs which are running complicated software (might be wrong though). One might say that because it is so old technology it is more susceptable to electrical damadge - I agree, but you know the inside me tempts to give it a try and investigate posibilities. I reckon that the logic might still be operable, but tinkered by the blown transistor (If you find such present). This could explain the camshaft possition sensor code. ECU tries to start the engine, but it does not start - during the start phase the camshaft sensor is the key components which dictates the ignition - I find some logic (but not complete though) the computer to declare that error (even more when internally the circuit malfunctions could help for that). Also the code is stored every time, not permanent. You can erase it. Also the code 47 you found initially stored in the ECU (the one which should not be there and does not have description), I think it coresponds to MB code 107 (if you read it with Hand Held Tester) - "Ignition dwell angle control output stage, short to ground". I believe the presence of this code whch is meant for another type of engine says that the ECU took serios mishap once, but the fact that you were able to erase it (and it never came back) gives me hope that it is not broken in its "core". Very complicated case study. A lot of ways to think towards it. Good example too! - That car could easily outlast any modern vehicle, just with elementary maintenance, but the era of cutting corners and being more "green" took its life :) I will place my final bet - With the replacement ECU and wiring harness repaired before any attempt to start it - it will run. I think it will be rough though - it has more than one issue under the chrome hood star.

[@PineHollowAutoDiagnostics]

Excellent comment!

[@notsoserious0944]

Even with all of your automotive sorcery, you can't kill the output of that infernal buzzer? Sheesh.

[@tullydog9047]

Happy Thanksgiving

[@PineHollowAutoDiagnostics]

You too!

[@josecondemarin9586]

Happy Thanksgiving Ivan !! Great follow-up video. Take care now, thanks 😊

[@londonglide]

Ahhh the well known rotting of the engine loom. Worse on 6 cylinders, but my 2.2 1995 had it as well.

[@baxrok2.]

A couple of commenters called harness in the first video. Seeing those bare wires was shocking for sure. Thanks Ivan!

[@chillybrit2334]

I'd not plug a known good ECM in until that identified shorted wiring is sorted in some way. To just plug the known good one in as is seems to me a sure way to end up with two fried ECMs. I'm sure they are neither cheap nor easily available. In fact the sight of that crumbling away insulation would have me worried about the state of the entire loom in the car. Hopefully (for the customer) it's just a symptom of wiring that gets heat soaked on top of the engine. Or maybe in the past that one coil had an issue, shorted, overheated its cables and that is the reason the insulation is all messed up (best case). But yeah.... plugging a "known good" computer into "known to have shorts" wiring..... I just couldn't. Fascinating case so far - thanks! :D

[@keltecshooter]

Some modern cars have wiring issues , we had a 2018 GMC with 6 liter engine with a ton of parts tossed at it for a misfire that turned out to be the injector harness insulation just falling apart right at the connector .

[@akhtarkh]

Mercedessource should be paying attention to this video.

[@pantherplatform]

Why come my 1995 town car has obd2 but the 95 mercs don't? Best winter car I've ever owned. 40 used brake rotors in the trunk on a set of bridgestone blizzaks seems to do the trick.

[@billrimmer5596]

I had a Volvo mid 80’s vintage. The injectors would short periodically and fill the crankcase with gas. Let’s just say there was a lot of tape involved with the fix. Other commenters talk about new repair harness. Would definitely fix all wires before plugging in new unit. The whole diag is a template on how to proceed with a problem car. Use of test light, positive and negative polarity. The scope. And, most importantly, how to research systems that aren’t well understood. Did the little light have to have a diode? And if a California car, it should have had an OBD 2 connector. They were required in 95.

[@PineHollowAutoDiagnostics]

Lots of variables, but no OBDII connector! Just a little red LED haha

[@dans_Learning_Curve]

Wasn't it 1996 OBDII was required? I had an '95 Windstar that was OBDII compliant but most vehicles were compliant in '96. I think Ford went compliant in '95 because Windstar was a new model that year.

[@DIYDaveOK]

I was wondering at one point if there was a 1995 Mercedes equivalent of a cam-crank relearn...

[@THEDRAGONBOOSTER8]

I was sure it was a bad wiper blade..It's in your hands now buddy . All the best..

[@PineHollowAutoDiagnostics]

Actually the wiper blade was bad! I installed a new one free of charge as a courtesy 🤣

[@samb3706]

I don't think the replacement ECM will fix the car. The harness appears to be the root cause, and I am afraid that installing the new ECM without repairing the harness could result in damaging the ECM. I think that the CKP anomaly is a separate issue, but, if that sensor's harness has crumbling insulation, it might be what damaged the logic in the old ECM. Good diagnostic sleuthing on your part, but the main event is just starting.

[@mikechiodetti4482]

On to part 3. How many wires are damaged and how long in the harness are they damaged?

[@whatsjeffdon3323]

Had a 95 C280 with the degradable harness. Was having issues with the car. Thankfully it didn't mess up the ECM. Replaced the harness with a new OEM harness and problem solved. If you can literally see the missing insulation and you like the car. Replace the harness.

[@stealthg35infiniti94]

If the wiring on the coils were shorted, those output Transistors probably took a big hit. In a lot of circuits the Final Power Transistors will die and not damage the preceding circuits. It's worth a try to replace the Power Transistors after you fix all the wiring and retry to start the car.

[@larrystephens7437]

Replace the three driver transistors! I just knew you were going to take it to the component level when I saw that computer on the bench.

[@hightttech]

The Mercedes Wagon Miniseries 👍. What is number on power transistors? I was very excited to see the computer has all discrete components and is not potted. Transistors can die many ways, not just dead short. Also, output from computer could have damaged clamping circuit that might interfere with signal path. While the turkey is cooking, you could pop out Q's and bench-test them. Excessive leakage through transistor to Gate/Base can damage or confuse control circuit(s). If they are BJT's, they are probably NOT driven directly by a smart component, but a smaller, more robust driver that can quickly saturate the power transistor. Anyway, thanks for great content, and Happy Thanksgiving.

[@melvinjones3895]

You went to Mercedessource this guy knows his stuff with MB I bet if you called him he would know but then. keep up the good test light work

[@ryanbradley4718]

Mercedes biodegradable wiring years, 91 to 96, this vehicle is degrading according to plan.

[@andrescastro4836]

Agree with Ryan. I know about that with a 1996 model 600 V12 almost lost to fire. Cheers

[@mikep95133]

Please repair the wiring to each coil first !! Triple check for shorts to hot, again. Everything has to be checked before the 'new' cpu arrives. Maybe the crank sensor or circuitry was also damaged. Can't wait to hear the answer !!

[@fredautos]

Ivann this purely a mystery and Indeed it worth a Thanksgiving !😊

[@yomomma9070]

Ivan, those wiring harnesses are junk. Others have said as well. And it's not just at the coils. It is gonna be throughout the entire engine harness(es). Your best bet if the owner wants it repaired is to get a replacement harness. Advance and auto zone used to offer these harnesses. I don't know if they still do. They used to be about 1/4 of what Mercedes wanted. They were made by Delphi and very nice. You will be fighting and losing the battle if you try to repair it. Hope this helps. Happy Thanksgiving and good work.

[@bostedtap8399]

Celebrating thanksgiving with wiring insulation decomposing, is there a link?. Great work Ivan. Best regards from the UK.

[@zx8401ztv]

I would have replaced or insulated the bad wiring before risking a computer, tape is cheap for a test. Check each coil resistance to make sure one hasnt gone short.

[@chillybrit2334]

At 7:00 we can tell you are engrossed with this investigation, that kind of parlance is not your norm for stuff you publish. Personally speaking, I applaud it :D

[@loz11968]

I know that Mercedes’ had an issue with the bio degradation of the wire being premature and they had to replace some engine harnesses I believe that was in Europe butI thought it was later than 95 not sure about the USA market though

[@JOMaMa..]

Same in North America those harnesses were junk..

[@JamesAllen300]

Ivan, you've only got to speak to Kent Bergsma at MercedesSource (youtube vid from part 1) to explain how bad the wiring harnesses are for this age of merc. The video link below shows Kent replacing the harness and explains the issue when mercedes went to degradable harnesses. kzbin.info/www/bejne/iXiTipeObdp8o8k&ab_channel=Mercedessource So in answer to your question Ivan, a replaced harness is going to be the only answer to this W124 problems.

[@Sandmansa]

In light of the new evidence, it looks like you are going to have to rewire the coil harness if you want to see that engine run right again. I've had to do a few in my day and it's usually caused by excessive engine heat. So, the damage should only go as far back as the coil cover. Now those ECM's are usually pretty robust. But if it gets cooked, you'll know it just by the smell alone. If you don't smell burnt electronics, then my money is still on that crank sensor.

[@Walczyk]

My Volvo 940 did this, after a massive nightmare of a diag, my dad finally admitted he replaced the crankshaft position sensor with one that had electrical tape, and never mentioned that part. Swore up and down he changed it already. Such an ass. Finally brought it up when the guy at ipd said it sounded like it was the sensor

[@Vespastendert]

Needs a new harness. Super common on the post 93 cars as they have biodegradable wires. MB trying to be eco back then bit them hard in the ass

[@bigjnsa]

This sounds like a case for Adrian's Digital Basement ;)

[@Vlda2393]

Those are NOT power transistors, but ICs. Transistors always have 3 pins. Check if there is any SMD fuse in a power path from ignition coils pins to those power ICs.

[@AP9311]

Ivan, well shorted can burn the driver. But if the harness can be fixed, then I'm sure you won't have the short again. But my question is, can this be programed to the vin? Or same part number? So my bet is yes it will work once the short is fixed.

[@ShanesGettingHandy]

Ohm out those power transistors and look for dead shorts between legs, even while installed. I wouldn't be surprised if one or more is toast and causing a whole avalanche of problems. Wouldn't be impossible to replace them.

[@LakeNipissing]

I've had the biodegradable wiring harness issue on my 1993 300E 2.8 . . . wire insulation went to crumbs / dust inside of all the looms. rough idle / stalling. Had all of that changed... car ran great for years, then the short harness for the throttle body failed. Fortunately there is a guy on KZbin who rebuilds your throttle body with a new integral harness if you send it to him. EPIC FAILURE for Mercedes to use biodegradable insulation.

[@deweydodo6691]

I would not hook up a good ecm to those possible shorted wires

[@somerandomguy3868]

Not just a new ECM but a new coil harness and then maybe

[@scottmcintosh2988]

One must fix replace the coil wires as to not dammage the new computor .

[@Dirtyharry70585]

Without new wiring, bet you’ll let the smoke out.

[@wrdcc01]

Replacement coil pig tails available from MB to sort this with 1m of cable.

[@rossastra16v]

Maybe worth checking the crank sensor wiring loom. This seems to be a common mercedes problem . Mercedes Benz used biodegradable wiring harnesses from 1991-1996, resulting in electrical problems caused by the insulation crumbling away over time.

[@dans_Learning_Curve]

Took 5 years for them to get enough failures to change wire insulation?!

[@jutto64]

Coil windings failing, usually starts as an intermittent issue. Resistance test of coil windings?

[@dayntubee]

Common issues with deteriorate wires. Keep playing with it long enough and it will rub off

[@lonwillis783]

Wow Ivan I accidentally unsubscribed from you. Great diagnosis! 👍😊

[@neilmurphy845]

Is that Mercedes the one they used biodegradable wiring

[@PineHollowAutoDiagnostics]

Must be 😂

[@micahap1559]

I didn't see part one but what I'm seeing appears that you only need to rewire coil wiring. It really shouldn't destroy the output transistors if it's a decent design. It also will not run with the bad wiring. You should repair the wiring first then test.

[@billziegmond4943]

I think the ecm is damaged. However I think there is something else going on wiring wise. There is power back feed going on somewhere else is my concern.

[@joelgrigsby96]

Those Mercedes with biodegradable wiring harnesses should be scrapped out and used for parts. What a short sighted move by them!

[@iDIL53]

Perhaps while waiting for a new module - check the wires and repair them first. you don't want to "fry" the next computer if the wires were indeed shorten due to crumbling insulators

[@nct9466]

Was it Merc in the 90s that used biodegradable insulation or something less pollutant? In NZ we use to get used cars from Singapore and their engine harnesses would go totally bare due to high under bonnet heat plus bring in the subtropical climate would just fall apart. Hence sold off cheap to New Zealand

[@phareztrinimand]

Hey did you see any diode between the transistor and output to the coil, I know the transistor has a diode but it can't protect a direct short for that long

[@psdaengr911]

Since you've identified and obvious bad cable that most likely was shorting ougt the ECM, I can't see plugging in another ECM until at least that portion of the harness is repaired.

[@PineHollowAutoDiagnostics]

My thought too. These ECMs are not cheap, and very hard to find!

[@jessicav2031]

I have no doubt that the drivers could be fried, but there is definitely also something wrong with the crank sensor! I would rather fix that first. Who knows if the computer is even making an attempt to fire the coils right now, seems doubtful. Wait, hold on! Did Ivan actually decide "this computer seems to be complaining about something I don't think is the problem, so I will replace the computer"? Isn't that classic parts-changer thinking? Is there some potential explanation for how a shorted driver could cause a crank sensor code? Seems impossible, so replacing the computer has to be the wrong first move doesn't it?

[@PineHollowAutoDiagnostics]

Jessica, you would excel in this field with your logical approach! Yes, that "code 24" was bugging me from the very beginning, but the scope shows a beautiful crankshaft waveform!! This doesn't compute in my head...never seen such a scenario before ;)

[@jessicav2031]

@@PineHollowAutoDiagnostics Hey, we all screw up right? I have learned a lot about this approach from your videos and even taken it into other fields of repair, I think it is generally applicable to all repair. Darned "modules" have such complex behavior that it is too hard to know what is going on. A family member has a GMT800 Yukon and the rear airbox hot/cold actuator wasn't working. I swapped the actuators and the problem stayed in the same place. I checked all the wiring between the module and the actuator and it was all good, no opens or shorts to ground or power, the 5v reference, ground and power were good, and the input/output signals matched the data stream for the 2 seconds that the module tries to operate it before throwing a code. Module power/ground also good. I even bench-tested the actuators using three power supplies and they worked perfectly. Must be a bad module right? Ordered a used module on ebay (naturally nobody has stock of replacement modules), throw it in, same problem. Uh oh... My new theory is that there is junk inside the box and the computer doesn't like the movement range of the door. But, getting into those boxes is a huge pain so I haven't gotten to it yet (it has some smell coming from it so it has to be done anyway at some point). Unfortunately, it is all one "range/performance" code and the movement FEELS fine by hand. And this doesn't completely match the symptoms either, when reset the module seems to just command the actuator to constantly move to one direction until it jams (yes I know these things have to be clocked, I have to reclock it everytime it does this, I know I have clocked it correctly based on measuring the feedback potentiometer and also the fact that it works fine when put in the other position). But I am not going to just assume I got a second module with the same problem, better to not make the same mistake twice :) Anyway, my point is just that weird failures can get complicated when we don't know what the computer is thinking, and what can we do? :)

[@josephwash109]

I noticed on the previous videos that some of the bolts on the engine are rusty, so the car's been exposed to salt. Is it possible that a computer ground is faulty? Since the ECM can set a code consistently for the CKP sensor, perhaps it doesn't have a critical reference ground to pick up the CKP signal. Those are some tough-looking transistors, so they could probably tolerate a few direct shorts before burning up for good. I'm hoping Bosch designed that ECM well enough to survive some abuse.

[@pookatim]

I would want to know what cooked the wiring harness like that. That's a lot of damage.

[@kevinbarry71]

I believe that was an example of Mercedes biodegradable wiring harnesses.. Wonderful German engineering