M103 Crank Sensor Replacement

This is a walkthrough tutorial of how to remove, test and replace the crankshaft position sensor at the rear of the M103 Mercedes-Benz engine.
This information and instruction is simply meant as a guide and look into what is involved to do this repair.
Use of the material shown in this video is to be used at you own risk as I am not responsible for any damage done to your vehicle from use of this information. This procedure should only be done by trained and experienced automotive technicians.

[@1969RAJ]

Great video - I tried this procedure, before (last year) - failed as the bolt holding the CPS was seized. Anyway, this is a great video and very clear! You did a great job to get your camera to focus etc... One tip if anyone is trying this. Be very careful not to break throttle assembly through lack of care...

[@MercedesTech]

Thanks, yea the Allen heads usually strip out, that’s why I try to spray them with some kind of penetrating fluid or work them back and forth first

[@1969RAJ]

@@MercedesTech Yes, that bolt was so freaking tight, I applied WD40 to loosen with no luck and too applied much force and just chewed up the allen bolt recess... That sensor is in such an awkward spot. Not sure why the bold head is made of a soft material (brass?) too... 🤦‍♂️ ( I think Mercedes may have used an impact wrench or heat to get it out... It was an expensive repair. Wish I could have done it myself, because the job isn't too mad, it's just a question of getting into that awkward spot and then routing the new cable through.

[@MercedesTech]

@@1969RAJ Exactly. Poor choice of material and bolt head. I learned my lesson removing the cold start injector that is held in by the same fasteners. I was replacing the idle control valve hoses and was only removing it for better access. Ended up having to drill and EZ out one or both of them...

[@VITOSGARAGE]

Just subscribed. Great video. Thanks for loving and saving old school Benzes. I have a W126, W123 and W210. Best cars ever made! I have lots of videos on them too. Take care

[@MercedesTech]

VITO'S GARAGE Thank you! And thanks for subscribing! I have a w126 and a w201 (in my cover photo). I prefer pre-2000 Mercedes for the most part, but love them all. I’ll be sure to check yours out. Cheers

[@MAGNESIUMBURN]

Thanks for taking time to do the vid and post, need to do this as well...

[@MercedesTech]

Your very welcome, glad it helps

[@JOHNVASSIL]

Great video Raj and very informative too. What resistance do you observe on the new CPS with a warm engine, and what is the acceptable range between hot and cold engine please?

[@aomar9449]

Awesome video, very well detailed thanks!

[@jackfortunati9453]

Excellent. Hard to find info on where this damn sensor actually lives, thank you for posting. My car shuts down when the temperature under the hood gets too high---idling in traffic! Super annoying. The resistance must go to infinity at some temperature, thanks for doing that experiment with the heat gun. Also: Sorry your repair didn't work. Did you open the distributor cap and get the humidity out with some contact cleaner? Even a new cap can get a small amount of moisture condensing inside and short out the ignition--happens often to me. Also happens to my Mercedes 500SL, that has 2 caps for each bank of cylinders---happened just yesterday, pulled distributor caps, sprayed MAF cleaner, replaced and it fired right up. Perhaps putting some RTV on the distributor cap is a good idea on these cars.

[@Petrolhead350cui]

My w201 1.8 has a bad cold start, warm start is a bit better. I ordered a new crankshaft position sensor, cause I almost renewed everything else. Hope it will make a difference.

[@davidbrown4868]

Nice video. I am having trouble pushing the sensor into its hole. Pretty tight fit and can't get enough leverage to push it in.

[@MercedesTech]

I’d try my best to clean the hole with brake cleaner or similar. You could also then try to set it in there to start, then VERY CAREFULLY, use like an extension and tap to in lightly.

[@muhamedislamovic7088]

I was trying to pull a same sensor from 91 190 2.6 it broke the top piece of and the body is still stuck in block what do you recommend to get the piece out it looks like it is rusted from a block and I still got that metal piece of the sensors inside with a plastic body in block is it ok to use torch or heat gun to get that plastic melted down a little so that the broken piece comes out of course using a wise grip pliers on that broken metal piece?

[@ademtrucking2107]

Do you have any idea why my 190e breaking the sensor you just changed when I put the new one in will not start and will breaker it

[@xaviergonzalez5145]

Thank you! I have an w124 260E, M103 engine. Your car has one CKP sensor or two?

[@BMWyCia]

My 1986 260 has one at the rear and one at the front as well. I believe the front one gives dwell signal that gets translates into the rpm of the tachometer.

[@patrickrichards1547]

Great video! Very informative. Just a question if you don’t mind. I am currently having a warm start issue car runs fine when cold but feels like it’s misfiring when warm and almost stalls when you come to a stop and does not turn on once the car has been turned off. I thought fuel so changed the fuel filter but fuel looks fine!. I have replaced spark plugs and spark plug wires still the same thing. Heard people on forums say it could be coolant temp sensor so I replaced that and still have the same issue. so I don’t believe the car is getting too much fuel I don’t think fuel pump is bad either cause it wouldn’t start on cold starts if that were the case. Do you think cps has gone bad? And you said the crankshaft position sensor didn’t fix your warm start issues. So that being said what fixed the warm start issue? And is getting a new crankshaft position sensor worth it? Thanks.

[@patrickrichards1547]

I also heard something about brake booster vac lines that sometimes they can get clogged. Should I start there before buying a crankshaft position sensor?

[@gbenz6494]

Where can you purchase Crank Position Sensors (CPS) for an M103 engine? Is there a good aftermarket sensor out there? The Genuine Mercedes CP sensors are NLA with Mercedes.

[@fb3824]

Thanks for the video. Questions. Why didn.t you try the heat gun on the new sensor? Seems like a lot of work to remove the old cable and run in the new cable, so why not just snip the ends off the old one, and run the new cable via more direct route?

[@MercedesTech]

I could've snipped the old sensor, but I have a habit of trying not to destroy old parts due to working at the dealership so long and having to turn parts in or give to the customer. Also just in case they're not totally bad or I need to reinstall it for whatever reason. In regard to your other question, I also like to install parts the factory route and method to keep it clean and stock. Anyone is of course welcome to cut the old part and install the new part in anyway they find that works "better"

[@MrTommy2977]

It’s not a Kia

[@BerlinettaFerrari]

My R129 300sl is cutting out at 4krpm, do you think that the crankshaft position sensor is the issue?

[@MercedesTech]

6SPD V10 Sorry for the late reply, but I suppose it could be, I would expect crank sensor to cause more hot starting problems than anything. For your issue I’d probably suspect that it’s something more to do with the air flow potentiometer.

[@theundergroundlairofthesqu9261]

Ugh, that cable routing is a pain! I need to check my W124, I thought the crank sensor was up by the crank pulley. Good news for nerds, those Mercedes zip ties are still available from the dealer in 2022. At least, that's what my guy says, I haven't received my box yet. Also, about five years ago, he got me some new Omega-shaped clips like you're tussling with here. It's very cool to be able to get almost any part you need for decades-old cars. Sorry about your salted roads! You wouldn't want to see what I'm disassembling right now, you'd be jealous.

[@Heve62]

Is this possible/easier to do from underneath on a lift?

[@marionietorosales7039]

Hi, nice videos, if you can help me im searching a rebuild kit for my e 300 engine M103.980, did you know where i can get those parts? Thank you

[@aidenwebb3638]

Did the car run before changing the sensor. I have a car that cranks but won’t start. Could this be the problem?

[@MercedesTech]

The car ran before the repair. Just ran poorly once warmed up.

[@codyloosle7415]

how did you find out it was bad my car randomly cuts out at 2k rmps

[@BerlinettaFerrari]

cody loosle Did you figure out your issue? Mine is cutting out at 4K rpm, but only in second gear....

[@MercedesTech]

cody loosle at 16:40 you can see the test method of the crank sensor cable, which can be done with it still in the car. Mine was actually not bad(or bad to where it was causing my issue) I ended up replacing the fuel distributor and adjusting my fuel mixture.

[@daniellitton4140]

Does a m102 engine 230e also have a crankshaft position sensor? thank you for information

[@MercedesTech]

I’m not sure, as the only M102 engine I have that I work on is a 16V bolted to a 5 speed. I can check that later though, don’t know if it would be the same for an auto

[@fritolay8668]

Great video thanks. I believe I found the culprit 🙂

[@MercedesTech]

Awesome! Glad I could help

[@fritolay8668]

@@MercedesTech By the way, at what specific range of ohms, you'd consider the sensor is bad?

[@MercedesTech]

@@fritolay8668 I’m not sure as to what a spec would be. But generally when the sensor is hot, it will just show OL on a meter meaning there’s an open.

[@TrainerTakumi]

thank you!

[@MercedesTech]

REDKILLER always welcome! 👍🏼

[@donjuanmurray4957]

I tried this on a w124 and the plastic broke off please any tips on getting it out it's a m104 engine

[@MercedesTech]

So your saying the magnetic end that goes in the back of the engine broke off?

[@donjuanmurray4957]

@@MercedesTech yes the plastic top part broke off any help or ideas?

[@MercedesTech]

Depending on space you can try and drill it or something like and ez out. Otherwise if it’s all plastic you can try sticking a red hot needle or something similar through the plastic and let it cool so you have something to pull on

[@donjuanmurray4957]

@@MercedesTech so do you think I could drill a concrete screw behind the engine with long extension and a universal joint? I would like to find a way to heat it up but that's looking like it's outta question

[@MercedesTech]

@@donjuanmurray4957 yes, if you can find a way to get a screw in it, that should allow you to have something to pull it out

[@barisakarca2608]

W124 300ce bei Vollgas hat kein Leistung und ab ca 4000umdrehung ruckelt

[@RicardoMartinez-kr5qk]

That's way more access then what you would have in say a w201

[@MercedesTech]

Yea. This particular job is real tight. I know that on the w124 and w201 the firewall is much closer to the engine/transmission. A buddy of mine and me removed 722.3 transmissions from all three configurations and the w201 was by FAR the hardest. mainly because the firewall gave limited access to the bell housing bolts.

[@RicardoMartinez-kr5qk]

@@MercedesTech yes sir, you get used to it but only after doing it several times, my w201 is on transmission number 4🤣🤣

[@MercedesTech]

@@RicardoMartinez-kr5qk damn, we were rebuilding the three we messed with. B2 band broke in 2 of them and reverse clutches went out in the 3rd

[@RicardoMartinez-kr5qk]

@@MercedesTech yeah, the b2 band seems like a weak point for these boxes, I've been tempted to re- weld a b2 band since they always seem to break at the factory weld spot.

[@MercedesTech]

@@RicardoMartinez-kr5qk Yes, definitely. Let me know how that works out if you actually try that lol

[@borntolate1]

WOW HE IS LIKE A PIG AT A POTATOE .SO HAMFISTED ...