Z06Vette.com - Corvette Z06 Forum - Trouble Passing Emissions With History Code 10-P0300?

BLEUBYU · 08-01-2007, 08:36 AM

I live in Va, where emissions compliance is done through a scan of the PCM. Last night I looked to see what, if any codes I have and I got one history code for the PCM of P0300. According to my manuals, it appears that this code can be triggered by an "individual cylinder misfire. A misfire rate that is high enough can cause damage to the catalytic converter. The malfunction indicator (MIL) will flash if converter damage conditions are present.

Since this is just a history code and I do not have any current codes, or flashing/steady check engine lights, will there be a problem with me passing emissions? This is the first emissions test I have needed since getting the LPE S/C package and some ECS work done.

I am sure allcars have occasional misfires, would not seem to be a big deal unless it was a continued high misfire rate? I do have all emissions equipment on the car.

Thanks..

TechSTL · 08-01-2007, 12:12 PM

Quote:

Originally Posted by BLEUBYU

I live in Va, where emissions compliance is done through a scan of the PCM. Last night I looked to see what, if any codes I have and I got one history code for the PCM of P0300. According to my manuals, it appears that this code can be triggered by an "individual cylinder misfire. A misfire rate that is high enough can cause damage to the catalytic converter. The malfunction indicator (MIL) will flash if converter damage conditions are present.

Since this is just a history code and I do not have any current codes, or flashing/steady check engine lights, will there be a problem with me passing emissions? This is the first emissions test I have needed since getting the LPE S/C package and some ECS work done.

I am sure allcars have occasional misfires, would not seem to be a big deal unless it was a continued high misfire rate? I do have all emissions equipment on the car.

Thanks..

That code is VERY common for cars with aftermarket camshafts. A tuner can take care of that for you pretty easily.

RocketSled · 08-01-2007, 12:42 PM

It could also be a problem with the Injector harness, or even a loose plug wire... Check the obvious stuff first. And there's always "glitch" as an explanation. Clear the code to see if it comes back.

itchynackers · 08-01-2007, 01:27 PM

I also have the LPE S/C package, and coincidentally, last week I got a History P0300 code. It hasn't come back yet. I just cleared it out and so far so good. You should be able to clear it out right before you pull into the emissions station and pass. (LPE also told me just to make sure all my plug wires were on snugly).

BLEUBYU · 08-01-2007, 01:41 PM

Thnaks to everyone for their replies. I think the mild ECS blower cam may have caused the code. Sometimes, when cruising in the upper gears at relatively low RPMS, the check enging light will "Flash" but never set, or stay on. I think if I clear the code, then make sure I stay in higher RPMS

on my way to get tested, I might be ok. I will check those plug wires also!

Now, is it true that I will need a certain number of "drive cycles" under my belt, before it can be tested?

No Doubt · 08-01-2007, 03:35 PM

Yes, you will need to complete a number of OBDII drive cycles before the code will be cleared from the PCM. This number varies depending on the code and system involved and can be as few as 3 or as many as 40 or 50.

Current codes (C) as displayed on the DIC are just that, current codes indicating the problem is ongoing. History codes (H) indicate a problem occurred in the past but isn't presently.

Technically, a history code should not prevent you from passing an emissions test as the problem it indicated has since been resolved. Again, it will go away once the required number of drive cycles have been completed if the problem does not return in the meantime.

TechSTL · 08-01-2007, 03:51 PM

That flashing CEL is from misfires too. Even a hobbiest tuner can take care of that problem for you. There are 3 tables (I think) that set thresholds for when that code is thrown. You probably just need to raise the threshold a bit at lower RPMs. You may be able to pass emissions by clearing the code and hoping it doesn't come back prior, but that only solves one problem (plate renewal). It won't prevent you from having the same issue.

Typically, if you have a problem with wiring, an injector or a coil, you will get a P030x where x = the cylinder that's having problems. P0300 = Multiple Random Misfires which means it's detecting a 'problem' on more than one cylinder.

BLEUBYU · 08-01-2007, 06:23 PM

OK, I was able to clear the one PCM history code. So tomorrow, I will start the first of a few drive cycles making sure the RPMS are up enough to avoid any recurrences - not hard to do! Then Sat morning I will take my shot at getting through the plug in emission test.

Thanks to everyone for their advice...