Code P0300 - Should I be worried?

[twiceVehk]

Took my brand new 5BW out for a mildly spirited drive last night, CEL comes on 5 minutes before home. This morning I call OnStar, they say it's code P0300 - emissions equipment malfunction and recommend service within 7 days.

I figure this is either nothing to worry about best case, or worst case the engine is missing and dumping unburned fuel into the cat and causing a code. The engine idles nice and smooth. Way smoother than the LS3 in my SS Sedan did. Power delivery is smooth, immediate, and unmerciful just as I would expect. Oil level and appearance are ok. Car has less than 800 miles on it.

Obviously I'm calling the dealer tomorrow, but it's Sunday and my anxiety is getting the best of me. Does anyone have any insight?

 

[jbawden]

That code is for random misfires. Given the stories of incompetence reported here, I get the anxiety , but odds are it will be fixed by capable dealer service center.

 

[WONT TAP]

DTC P0300 is for random/multiple misfires. I would make sure you've got good fuel and have the spark plugs inspected.

 

[Speed Racer 007]

Hope its an easy fix for you!

 

[sonny200]

What was the issue(s) & how was it remedied?

I got the same code after a track weekend. Have an appt with the dealer tomorrow. Will report back on the issue(s) & fix(es).

 

[sonny200]

1. Took it to the dealership & left it for them to figure out. They could only clear the code bc the engine had been cycled on/off too many times for the ECU to retain the possible cause of the code.(?)
2. Picked it up later that day & on the drive home, <2700 RPM & at WOT, the engine would stumble & be extremely rough such that I had to let off the accelerator almost immediately bc it was that alarming. In higher RPM's, no issues at WOT.
3. Brought it back to the dealer the next day.
4. They diagnosed #4 coil failure. What's weird is even though the engine was obviously misfiring at WOT in low RPMs, no CEL/code.
5. Replaced coil, spark plug & wire. (Under warranty.)
6. Got the car back & all is well!

 

[dinkman]

thats odd there was no cel for a misfire/bad coil but glad you got it sorted out

 

[MDM]

I always find it funny how common it is that the "system" won't retain the info needed for a normal repair. We all know that the "system" would sure retain the info if it was related to extra boost added from let's say a smaller blower pully.

 

[The_Ghost]

With GM's history of never being able to fix P0300 on any of my previous GM vehicles....this could end badly for you. Hopefully they figure it out and fix it. But from my experience with a boosted GM car, it could be:

- unmetered air getting in/out between MAPs
- bad plug(s)
- bad coil
- bad head gasket
- bad injector
- bad hpfp
- bad upstream/downstream O2 sensor(s)
- bad cat (but usually a P0420)


Or it could just be a bad PCM program like so many other GM vehicles with a very tight tolerance for mis-fire detection. Unfortunately there's a ton of things that can cause this code and it's not as simple as, "hey, this is it". Good luck to you! I would suggest starting to cruise other GM boosted car boards that have been around for a while. Like the Camaro ZL1, trucks, etc. Just jump in and search P0300. There's a lot more information on the turbo GM stuff for P0300 then the SC stuff.

 

[sonny200]

With GM's history of never being able to fix P0300 on any of my previous GM vehicles....this could end badly for you. Hopefully they figure it out and fix it. But from my experience with a boosted GM car, it could be:

- unmetered air getting in/out between MAPs
- bad plug(s)
- bad coil
- bad head gasket
- bad injector
- bad hpfp
- bad upstream/downstream O2 sensor(s)
- bad cat (but usually a P0420)


Or it could just be a bad PCM program like so many other GM vehicles with a very tight tolerance for mis-fire detection. Unfortunately there's a ton of things that can cause this code and it's not as simple as, "hey, this is it". Good luck to you! I would suggest starting to cruise other GM boosted car boards that have been around for a while. Like the Camaro ZL1, trucks, etc. Just jump in and search P0300. There's a lot more information on the turbo GM stuff for P0300 then the SC stuff.

Well, the vehicle has been running fine since they did the repair. I don't granny-drive so would've noticed something amiss. Keeping& will report back if anything changes.

 

[The_Ghost]

They diagnosed #4 coil failure. What's weird is even though the engine was obviously misfiring at WOT in low RPMs, no CEL/code.

So with GM and all other makes, you can "pend" a code. Which means that the computer detected an anomoly, and if it happens another x-times, the CEL will set. Many people don't know this. I had an issue on my other car where boost was cut in half, but no CEL. I would have a "pending" p2178 code for the HPFP. And it could pend for 10 miles, or it could set a CEL on the next acceleration. So keep that in mind....

 

[RChrisE]

1. Took it to the dealership & left it for them to figure out. They could only clear the code bc the engine had been cycled on/off too many times for the ECU to retain the possible cause of the code.(?)
2. Picked it up later that day & on the drive home, <2700 RPM & at WOT, the engine would stumble & be extremely rough such that I had to let off the accelerator almost immediately bc it was that alarming. In higher RPM's, no issues at WOT.
3. Brought it back to the dealer the next day.
4. They diagnosed #4 coil failure. What's weird is even though the engine was obviously misfiring at WOT in low RPMs, no CEL/code.
5. Replaced coil, spark plug & wire. (Under warranty.)
6. Got the car back & all is well!

Strange about the "....cycled on/off too many times...." response.

IFRC, Last time I was doing that kind of stuff it was in the 20 to 30 cycles before old events dropped off the computer queue. But that was years ago.

Chris E.

 

[Rob CT4-V]

I'm surprised it didn't pop a P0304 code if it was a coil failure in that cylinder.

At least it's running good now.