When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
After 120 months of ownership my 2010 S550 with 123,000 miles on issued me it's first ever check engine light.
A misfire that came out of the blue on cylinder #1 (P0351) the car began to run awful. I was down the road from my house so I turned around and went home. Scanned it, ran to Autozone and put a new coil in the #1 spot. Started it up cleared the code and went on my way. The car ran fine all day.
later in the day it through the check engine light again, but it was running fine. Scaned the car and I have a P0356.(ignition coil primary circuit of cylinder 4 is too low) cleared the code and it came back. The car is running fine. I checked the wires, and vaccum hoses they seem snug.
The coil packs and spark lugs were replaced at 64,000 miles by the MB dealership I bought the car from which was almost 9 1/2 years ago. My question is this, do coil packs tend to go in pairs or is this an odd occurrence? The car is running fine. Should I be looking at something else before I replace another coil pack? Tomorrow I'll do the swap and see if the code follows the coil pack. If it does, I'll have my answer if it doesn't what should I do next?
Swap the coil from cylinder 4 with another cylinder. If the misfire code moves to the new cylinder, you've confirmed it's a bad coil. If the code stays on cylinder 4, the problem is likely the wiring or connector to that coil. It's not unusual for coils of the same age to fail close together.
Merc are not an as incompetent bunch of cheating criminals are they might fist appear - they do not have just the one specification of designed to fail componentry (in this case ignition coils) - rather they spend billions on development to ensure the supplier production lines pump out junk with multiple designed in variable timeline failure modes....
I still have 3 original coils sticks at 19 years and 74k miles still working as well as a good brand new one
Then I have 3 that died at 50k miles 9 years in and were replaced with secondhand ones of indeterminate age still going strong
and a further two that died at 65k miles and 15 years, again replaced with secondhand Merc OEM junk from ebay, again of indeterminate age
I would suggest mine will out last many of the ones where people replaced all eight with new (designed to randomly fail) junk the manu loves to peddle
they are just a bunch of sharks trying it on - just like the the rest of the world - mainly because the Germans have taught them all this very effective business model over the last 35 years
I checked the connection on cylinder 4. It maybhave been knocked lose when I pulled the covers off. I cleared the code and it hasn't come back.
I decided Just for peace of mind I will replace the set. Ill keep a few of the old packs that I know are good in the trunk I case of a on the road issue. I never had a coil pack fail randomly without warning before. When I had a bad coil pack on my wife's GL550 it would occasionally stall, but never throw a check engine light. A pending lean code was present. It was a PIA to diagnose. The scary thing was that it would stall on the highway.
Last edited by The Thomas J; Nov 25, 2025 at 09:00 AM.
keeping the good ones as spares is sensible - u can swap one at the side of the road in 10 mins easily - and is far better then killing a CAT in a 5 mile drive with it missing like a pig
as for them dying - try a BMW - bikes lead the field used to manage 30k miles on the R1200 boxer twins - but things evolve - now many K1600 6 pot bikes will have them all start dying from 20k miles at any thing over 4 years - the week I sold my 2019 K1600 at just 10 k miles it missed like one was giving up on start up
as far as quality goes her ford vs my merc vs a BM bike - number of sparks before death - nothing suspicious going on here with German build quality !!!!!!!!!
Botus when the electronics sense a dead miss it turns the injector for that cylinder off. Hence; no dead cat.
it 100% could, and 100% should - but it 100% doesn't - so it does kill the CATs - just as half the diagnostic code descriptions love to explain "damages TWC"
After 120 months of ownership my 2010 S550 with 123,000 miles on issued me it's first ever check engine light.
A misfire that came out of the blue on cylinder #1 (P0351) the car began to run awful. I was down the road from my house so I turned around and went home. Scanned it, ran to Autozone and put a new coil in the #1 spot. Started it up cleared the code and went on my way. The car ran fine all day.
later in the day it through the check engine light again, but it was running fine. Scaned the car and I have a P0356.(ignition coil primary circuit of cylinder 4 is too low) cleared the code and it came back. The car is running fine. I checked the wires, and vaccum hoses they seem snug.
The coil packs and spark lugs were replaced at 64,000 miles by the MB dealership I bought the car from which was almost 9 1/2 years ago. My question is this, do coil packs tend to go in pairs or is this an odd occurrence? The car is running fine. Should I be looking at something else before I replace another coil pack? Tomorrow I'll do the swap and see if the code follows the coil pack. If it does, I'll have my answer if it doesn't what should I do next?
with a title like that after all those miles and time you should marry this car cause that’s a keeper .!!
good luck with the turnaround.!!!
Currently I drive: 2007 S550, 2009 ML350 and 2004 CLK320.
I still have 8 original coils that I've replaced a couple of years ago. Two of them gave me same symptoms as the author of the thread described. And I'm now sure now which two. Is there a method to test them without installing them back?
modern electronics / circuits don't usually respond well to simple resistance checks - but you will find slight differences across the pins on the coils - but you'll need some tail with the connector pins or there's no real chance - and document where you are
with a title like that after all those miles and time you should marry this car cause that’s a keeper .!!
good luck with the turnaround.!!!
She was a well mainatined 1-owner car before I became her guardian. I have taken very good care of her. I take car of all my children. My journey to finding and buying her is well documented on this forum. Back than this forum was a hot bed of activity.. Nearly every sub-forum had steady activity. It's a shame how much it has changed.
I replaced the coils. I did the plugs too. The plugs looked fine. Everything is done, and the car is running well. It feels a bit more peppy. The Autozone coil I had installed lasted exactly 5 days before it threw a code. It was $83. I'm going to try and return it. Not cool, Autozone. It sucked changing out everything out in my driveway in 38* weather. The space heater and heated scarf I was wearing helped. What was worse was that coil 4 fell apart in my hand as I was disconnecting it. The head broke off in the harness. I had a mild panic attack as I wasn't sure how to remove it. At first, it looked like the pins were damaged; fortunately, they weren't.
Last edited by The Thomas J; Dec 3, 2025 at 02:14 AM.
The Autozone coil I had installed lasted exactly 5 days before it threw a code. It was $83..
Lesson learned. Use OE parts :-)
Some years ago, I learned that the hardway. Replaced eight coils...then, replaced them all again one by one in about two months. Being as I have 36 spark plugs (in cars) in the garage. I keep coils handy. Fortunately, all the cars but the 300 take the same coil.
Some years ago, I learned that the hardway. Replaced eight coils...then, replaced them all again one by one in about two months. Being as I have 36 spark plugs (in cars) in the garage. I keep coils handy. Fortunately, all the cars but the 300 take the same coil.
The 300 is a recent purchase. I was wondering if the coils were the same, and said to myself they probably aren't because it's a 4-cyl. I am really enjoying the SLC. My wife likes it too. That forum is beyond dead. It has tumble weeds blowing around.
most stuff newer than the S class are so complicated to diagnose and fix - and people buying newer stuff have less common sense and technical knowledge - we are past a tipping point of throw it in a skip and move on
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
