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I have a 2008 C300 4Matic. As some of you may remember I was getting a code intermittently for 0987 (ignition coil on cylinder 4 has an electrical fault or open circuit). I always sort of knew it was electrical due to the randomness of it, but it wasn’t until about a week ago I actually got to start seriously diagnosing it. I found out the female socket that connects to the ignition coil pins was very loose on pin #1. I already went to the dealer and had them order a new socket replacement.
My question is, does anyone know the part number on the disconnect tool? I believe it’s the SLK 2.8 but don’t want to drop $60 on the wrong one, and the dealer isn’t able to help with tool part numbers since they’re “for techs only”.
Also, does anyone know the removal process for that elbow immediately behind the connector? I’ll need to remove it to access the rear of the socket and actually replace it, but I looked around and I don’t see any glaringly obvious way to remove or slide it off.
Lastly, just so I’m prepared does anyone know if the socket is crimped on? Or soldered? Logically I would think that crimping the socket on would be fine, but I haven’t removed it yet to take a look as it’s also my daily and I don’t want the socket to not click back in at all and then I’m out of a car until the part comes in. TIA
@TimC300 will probably chim in. Or maybe reach out to him. My engine is an M276, so I can't visualize what you are saying.
I’ll post a picture tomorrow morning of the elbow and also the loose socket for a reference. I would take one now but my fiancee has my car at the moment.
Sorry for the delay. Took this picture last week but completely forgot to post it here lol. I need any help on how to remove that elbow from the connector so I can access the pins from the rear. Thank you all.
Also, does anyone know if you can replace the pin without replacing the harness? I still haven’t found exact instructions on how to remove that connector, but I have seen one similar and in order to depin, you needed to break a plastic tab which obviously means it wouldn’t be reusable.
Im sure it can be replaced since there is a part # for it. When I look closely at a photo of the connector it looks like there is a slit down it, probably some small tabs holding it closed. (red arrows?)
I looked up the specific part# for the connector but cannot locate the specific one. I was looking in the manual if you scroll down to the bottom under "DIAGRAMS > CONNECTORS"
I started looking under "Power and Ground > Wiring Harness > Service and Repair > Removal and Replacement to see if i can find that type connector. Maybe you will have some luck.
Found a better close up photo. Looks like theres two part #'s, connector is made up of two pieces. The #'s match the two part #'s in the diagram.
- 0225457026
- 0005456084
I plan on replacing my spark plugs this spring. Is it really needed to disconnect the coils? Is there enough slack in the harness to just pull the coils without disconnecting?
Can see two tabs on the elbow part connector piece. Bet the come apart.
Found a better close up photo. Looks like theres two part #'s, connector is made up of two pieces. The #'s match the two part #'s in the diagram.
- 0225457026
- 0005456084
I plan on replacing my spark plugs this spring. Is it really needed to disconnect the coils? Is there enough slack in the harness to just pull the coils without disconnecting?
Can see two tabs on the elbow part connector piece. Bet the come apart.
Ive done spark plugs twice on mine. You definitely don’t have to unplug them, but I always did just for simplicity. Harness has a ton of slack though. Especially if you just took all the screws out for the ignition coils on each bay and then moved them all to the side at once.
I’m trying to replace one of the female sockets inside of the ignition coil connector. In order to access it, I need the elbow to come off so I can get to the wires from the rear. Having the elbow makes it look super clean and tidy in the engine bay, but impossible to access the wires and replace the socket without removing said elbow. That’s why I was looking for help with the depin process.
That elbow piece looks likes its basically a cover, two tabs hold it closed and it just folds open. Im not sure if mine has that elbow or its just the 0225457026 connector.
With the elbow off it looks fairly straight forward to push the wire part out. Can even buy a used one off ebay cheap to practice on.
You don't need to break the connector but I would just get a new plastic connector if you are depinning already. The correct tool is W220589019963. but you can make it work if you get a common two prong dismantling tool and a thin pick. You kinda need three hands doing it that way.
You need to go by VIN because the wire gauge may be different from production year to production year when ordering new terminals. It's very difficult to tell the crimp size on the smaller sizes like 0.5mm².
All the wire terminals are crimped on. If you said the pin is loose you can try to bend back the metal holding tabs. They don't just get loose by randomness. It could be the plastic housing has a broken lock too. I would try replacing the connector if that is the case so you can avoid modifying the harness.
According to the Carfax it shows the spark plugs being replaced at 80,000 miles at an MB dealer then it lists the spark plugs being replaced at 110,000 miles at the last car dealership that had the car for awhile. I now have almost 160,000 miles and I want to replace them. Sometimes at lights theres a slight vibration that annoys me. I've already run some Techron thru and still notice it, hoping new plugs will make it smoother. What plugs did you install? My operators manual says to use the non-resistor type and I finally got around to asking FCP Euro if the Genuine Mercedes are in fact the non-resistor type and they say they are. I havent checked to see what plugs are installed, im going with the Genuine Mercedes anyways now.
According to the Carfax it shows the spark plugs being replaced at 80,000 miles at an MB dealer then it lists the spark plugs being replaced at 110,000 miles at the last car dealership that had the car for awhile. I now have almost 160,000 miles and I want to replace them. Sometimes at lights theres a slight vibration that annoys me. I've already run some Techron thru and still notice it, hoping new plugs will make it smoother. What plugs did you install? My operators manual says to use the non-resistor type and I finally got around to asking FCP Euro if the Genuine Mercedes are in fact the non-resistor type and they say they are. I havent checked to see what plugs are installed, im going with the Genuine Mercedes anyways now.
Thats strange. Bosch told me in an email that they don’t make the non resistor type anymore and it’s been superseded by the resistor type.
I actually did an experiment and I ran the NGK plugs recommended in the manual for 10k miles. I switched to the Bosch plugs about 2k miles ago and I’ve consistently gotten 2mpg better with every tank of gas I’ve had since then, all my normal commute. The NGK’s worked good but the Bosch definitely has improved my fuel economy, nothing else has changed as far as the engine.
I’m going to have to run to the dealer and ask to see one of the plugs and find out if they’re the one in the manual. If so, I’ll have to give those a shot too!
Last edited by hmclaughlin67; Apr 16, 2025 at 07:35 PM.
That elbow piece looks likes its basically a cover, two tabs hold it closed and it just folds open. Im not sure if mine has that elbow or its just the 0225457026 connector.
With the elbow off it looks fairly straight forward to push the wire part out. Can even buy a used one off ebay cheap to practice on.
Thank you for the heads up about the seal. I hadn’t even thought to get a replacement one of those too. I got the new socket, all I need now is the tool. I found it from Kostal for like $40 which is much better than the $180 for the MB tool.
You don't need to break the connector but I would just get a new plastic connector if you are depinning already. The correct tool is W220589019963. but you can make it work if you get a common two prong dismantling tool and a thin pick. You kinda need three hands doing it that way.
You need to go by VIN because the wire gauge may be different from production year to production year when ordering new terminals. It's very difficult to tell the crimp size on the smaller sizes like 0.5mm².
All the wire terminals are crimped on. If you said the pin is loose you can try to bend back the metal holding tabs. They don't just get loose by randomness. It could be the plastic housing has a broken lock too. I would try replacing the connector if that is the case so you can avoid modifying the harness.
I was only going to depin the one that’s loose, but I’m debating replacing the connector anyways in case that’s the problem like you stated. I’ll probably just get the connector as well and then if it turns out the pin is tight to the wire, I’ll replace the connector instead.
I would be hesitant to just replace one of the pins. If just doing one then that wire will be shorter and im thinking the other 3 wires will end up being bunched up in that elbow, also probably putting tension on the crimp. I would snip all the wires so they are the same legth.
Theres tons of info in that manual. From the diagrams I think the pin connector has to be crimped onto the seal also. I could be wrong.
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