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So for the past few days, I've had the check engine light start flashing when the battery finally dies and it kicks into engine mode. It's also stayed on twice after it's flashed. Checked the code with my OBDII scanner and the first 2 times it was P0303. Last night on a a test drive, I could only get it to flash, not stay on, and the code that showed up was P0300pd. I tried to swap coils, but realized it was a weird "all in one" coil pack that I've never seen before and I couldn't just swap colls to see if # 3 coll was bad. My engine only has about 30k miles on it, the rest of the 67k is all battery miles. So I can't imagine the plugs would need changed already, since they're supposed to be good for 100k.

One interesting thing to note... I have had this wheel vibration that's gotten worse over the past month or so, and it's gotten pretty bad just recently, almost maybe coninciding with the CEL. I read in the manaul that a flashing CEL could be caused if I used different tires than OEM, which is weird. I'm wondering if the vibration is somehow triggering the code/CEL??? Anyone ever experience anything like this? Any suggestions? In the mean time, I guess I'll fix the wheel vibrations and see if that fixes it. If not, I'm thinking replace the "coil pack bar" or whatever it's called and see if that does the trick. Any thoughts or ideas are welcomed.
 

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Year Model?
 

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So for the past few days, I've had the check engine light start flashing when the battery finally dies and it kicks into engine mode. It's also stayed on twice after it's flashed. Checked the code with my OBDII scanner and the first 2 times it was P0303. Last night on a a test drive, I could only get it to flash, not stay on, and the code that showed up was P0300pd. I tried to swap coils, but realized it was a weird "all in one" coil pack that I've never seen before and I couldn't just swap colls to see if # 3 coll was bad. My engine only has about 30k miles on it, the rest of the 67k is all battery miles. So I can't imagine the plugs would need changed already, since they're supposed to be good for 100k.

One interesting thing to note... I have had this wheel vibration that's gotten worse over the past month or so, and it's gotten pretty bad just recently, almost maybe coninciding with the CEL. I read in the manaul that a flashing CEL could be caused if I used different tires than OEM, which is weird. I'm wondering if the vibration is somehow triggering the code/CEL??? Anyone ever experience anything like this? Any suggestions? In the mean time, I guess I'll fix the wheel vibrations and see if that fixes it. If not, I'm thinking replace the "coil pack bar" or whatever it's called and see if that does the trick. Any thoughts or ideas are welcomed.
Certainly you would want to address the wheel issue if it is getting bad. Any CEL's as a result of wheels would likely be triggering traction control messages for the most part or possibly anti-lock brake messages unless it was real bad and causing some weird drive train issue. This may be the case if you are actually experiencing a really bad wheel bearing issue that might be putting stress on the drive train. Has your mileage gone way down or have you noticed acceleration or braking changes aside from the change over to the gas engine?
 

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Discussion Starter #4
Ok, so the manual actually says, "...the replacement of the original tires with other than those of the same Tire Performance Criteria (TPC) can affect the vehicle emission controls and can cause this light to come on."
 

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Discussion Starter #6
No, no other changes noticed really, besides the vibrations (which are coming from the rear right) and the CEL.
 

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Flashing and Solid Check Engine Light - P0303 and P0300pd

PO300 is a general code. PO303 is a misfire on Cylinder 3. Pull the spark plug and look for carbon tracking along the insulator. If it appears clean I'd bet you have a dirty fuel injector. It happened to me on my Prius. I did the easy stuff first. Plugs and coil position swaps. But those yielded nothing. I tried a few tanks of fuel injector cleaner which yield sporadic results. Ultimately I changed the injector on that cylinder and it FIXED the problem. No more CEL


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You might want to fix the vibration first and reconfirm (especially if you are not really feeling/hearing/detecting a steady misfire as being present)
There has been cars where a bad vibration affected the misfire diagnostic
The diagnostic detects crankshaft speed irregularities via the crankshaft position sensors continuous signalling and chassis vibrations can certainly impact this

WOT
 

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Discussion Starter #9
So the vibration was beacause apparently the rear right tire had separated inside. Got new tires on it now and the vibration is gone, but the CEL still comes on intermittently, blinking, with engine vibrating when in comes on, etc., still with same codes. My wife said she heard some sort of brief knocking during the engine vibration the last time she drove it. Haven't driven it since. Guess I'll start with spark plugs, then new "coil pack" since you can't swap them around. Will report back.
 

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If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards,P0300 will set.

DTC's P0301-P0304 correspond to cylinders 1-4. In this case cylinder 3 is misfiring enough to set the DTC P0303

When the MIL is flashing, the fuel injector may be disabled on the misfiring cylinder to protect the catalytic converter.


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Discussion Starter #11
Took it to the dealer since I was still under the 5yr/100k mile powertain warranty. Dealer said there's a memo out that this code with these symptoms on 2012 Volts means the cylinder head needs replaced, so they're doing so. Part should be in tomorrow. I wonder if they fixed whatever caused this to happen in the first place. If not, might be selling this. No way I want to have to pay for this again out of pocket! Probably not a cheap or easy fix.
 

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Ask for the service bulletin number. Head replacement is very extreme for a cylinder misfire.


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Discussion Starter #13
The service bulletin is PIP5201A. Got it back. $2,300 repair - done just under warranty! Dodged that bullet!!!
 

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I'd like to know what makes this a 2012 Volt specific issue? Did the they change the head design for 2013 model years. I found the service letter but could not access the full document without paying a $5 one time fee for that info. The title was " Cold start misfires MIL P0300". (Jan-25-2017)


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Discussion Starter #15
I'd like to know what makes this a 2012 Volt specific issue? Did the they change the head design for 2013 model years. I found the service letter but could not access the full document without paying a $5 one time fee for that info. The title was " Cold start misfires MIL P0300". (Jan-25-2017)
I'll buy it and post it so we can all see what it has to say.
 

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I'd like to know what makes this a 2012 Volt specific issue? Did the they change the head design for 2013 model years. I found the service letter but could not access the full document without paying a $5 one time fee for that info. The title was " Cold start misfires MIL P0300". (Jan-25-2017)


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I'll buy it and post it so we can all see what it has to say.
Nothing in the head was redesigned as far as I am aware (and nothing stated to that within the bulletin)

In fact, the preliminary bulletin is comprehensive in it's directions to inspect NUMEROUS potential causes for a "cold start misfire" including ignition and fuel system checks.

Instructions to perform "top end" cleaning is an item mentioned specifically deeper into the document, and if unable to alleviate the misfire after doing so (and all previously listed diagnostic checks) the head it to be replaced and the customer advised to use ONLY TOP TIER FUELS (specifically formulated to help keep injectors and top-ends free of carbon deposits)

Again, no head redesign or anything and AFAIK it's the same part number. But I too am curious as to what makes this specific to the 2012 models (but will try to find out)

WOT
 

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This is a good tutorial on what I think was going on with OP problem and ties into what WOT was explaining.

http://www.aa1car.com/library/intake_valve_deposits_gdi_engines.htm

The very first sentence in the last paragraph of the article is what I think happened here. Prompted by the fact it was still under "Warranty"


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