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Hi there I have a 2012 s550 with 85k miles on it, I purchased the car back in December of last year with no problems, when I got the car I had a full tune up, oil change, spark plugs, coil packs, and also filters. everything has been running smoothly until today, I had a check engine light on and I scanned for codes and I got this code P0301, it says it’s misfiring in cylinder 1. Is this something I can fix myself? I took it to the shop to see what they say. In the future are there things I can do to fix this on my own? I heard coil packs go out a lot on these cars.
When were the plugs last changed? You have to pop the air filter housings off, but on the 5.5 M273, swapping all 8 plugs and coils will take an hour with a stop for a wobble pop.
Can't speak for the later 4.7 turbo lump, but fundamentally it shouldn't be much harder.
Swap the affected coil for the one opposite. If the code moves then it's the coil, if it doesn't it's either the plug or the wiring.
Plugs, change all 8 at the same time. Always.
Coils, prudence would suggest changing all of them, but equally there's no shame in swapping them as they fail.
plugs and coil packs were all changed last December 2025
Genuine or aftermarket?
If genuine and a coil has failed, it should be warranted for at least 12 months if fitted by a certified shop. In which case start by taking it back there.
OP did the shop explain how they arrived at a bad injector?
If the answer is the coil got moved to cylinder next to one that misfires and plug got moved to cylinder next to that one and misfire didn't move.... Than I agree; ASSuming they have verified that the injector is getting a pulsed signal to operate.
Smart move now being to give it a complete set of injectors rather than play whack a mole with them as they fail individually.
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P0301 Code?
