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Discussion Starter #1
Well; at 12k miles I have the p0300 error code gremlin.

In doing my research for this Gremlin on my 2012 SRT 392 I found a few things out.

First; the car is not broken or in need of repair. What is happening is the ECU is counting all the misfires from startup and from point A to B. Due to emissions the engineers programmed a very lean idle F/A mixture. So the ECU is counting this banging around as a real issue.

Second; many, many cars were torn apart for no reason by parts changers or in a quest to "Do something" about it.

Its in the ECU code. There is no gate in the software to wait until warmup completes to open up the counter gates and start counting mis-fires towards an error code. I asked the dealer to update the engine code due to this issue. Yes; I'm Anal about this car, error codes drive me nuts. So they put in a more modern engine code P/N ending in AF, and did a little more odds and ends confirming the car is not broken. So anyway I think that's 2017 485hp code, but until I get to the strip; it fells like about 30hp more than I had. But once again it came back, so more looking and internet sleuthing and discrete questions to Hotrod guys at the dealerships. Come to figure out Dodge doesn't see this as an issue warranting a software fix.

So what causes it and how to fix it? Well Dodge has to fix the code in the ECU. What causes it; driver habits with cold starts and not driving anywhere, and the mis-fire counter gets you. I found it takes 10 / ten key cycles with at least 8 miles between starts so the code will clear itself without any action on your part. I just have to accept that if I do only short trips it will throw a code, part of owning an SRT with quirks.

I hope this post helps Owners and maybe Dodge dealers will stop throwing parts at a problem that is not hardware, and use some customer relationship skills instead. In the meantime I am enjoying the new code! :smile:
 

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Hi there,

Had a similar issue, codes have been cleared by the dealer and they’ve asked me to wait to see if it comes back again.

How long ( roughly ) did It take for the CEL to come back on? I’ve driven it for 70 miles now over a 1 week period with a mix of short (4-5miles) and medium (20-30mile) Trips. Does it usually take longer than that to trip the CEL?

I haven’t been hammering the car, just driving it normally.

My code was specifically P300 and P308.
 

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Discussion Starter #3
It doesn't take long, the more you idle cold, the faster you see it. You didn't state your mileage, but mine needed spark plugs due to lead fouling at 17k miles. I used nothing but Shell brand 93 octane and at the track royal purple octane booster (glass pistons) since I am really hammering it and hitting the rev limiter.

I suspect the p0308 code is from a pair fouled plugs. I had the dealership replace all sixteen plugs due to a noticeable loss of power. The plugs are expensive and I could have done them myself but guys there working there are really cool. The plugs are really really cold for the application and that may have something to do with them fouling out so early. I was told they do not do many 392's since it was such a low volume engine.

I get the car in motion as quickly as possible after I start it to get it hot and limit what I now know for a fact, is the counter gate is opens upon startup and if you do not move sooner rather than later it will pop a CEL code. Only long drives clear that counter to back to zero for a fresh start at zero misfires.

I have a special magnetic thin and long spark plug socket just for this engine so I can play if needed.

I do not think your car is broken. maybe it just needs plugs and a different driving regimen.
 

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Its in the ECU code. There is no gate in the software to wait until warmup completes to open up the counter gates and start counting mis-fires towards an error code.
Interesting, where did you hear that? I was under the impression the monitor for misfire starts when the adaptive numerator is updated (per the FSM) which occurs when the engine goes into close loop. I have done several cold start logs and these cars hit CL pretty quick...usually well under a minute. Some of the tables available in HP tuners lets you see some of the misfire monitor settings and what is interesting is the min RPM for detection is 384rpm and it is disabled if the ECT is below 19F or ambient is -9F.

I think the reason why FCA might be throwing parts at it is because in 2012 there was a TSB 09-002-14 for 3.6L equipped models where the cylinder heads were the culprit.

Update:
Looks like the adaptive numerator sets when the key is simply "on" and not when the system hits CL which aligns with what you said skypilot. But it now makes total sense why the system looks for misfires almost immediately as it wants to prevent catalyst damage. BTW looks like spelling isn't FCA's strong suit either. :)
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