04 Sierra P0300 Problem

[gbayfisher]

Hi guys,

I have a 2004 gmc sierra 2500 LD, 6L, 4x4 50,000 miles. Been setting a random misfire code for a couple months now, and I am trying to narrow it down.

What I have scanned so far:

-p0300, only code ever pulled thus far.

 

Seems to idle very well, has an ever so-slight cold start "stutter" or slight shake if i can even call it that.

I have owned 4 6L'ers before and they all seemed to have had the same cold start/ idle like this one, so i don't think it is a problem.

I have never felt any type of stutter indicating a miss at start up or cruising speed. slight ping at high rpm (4-5500) on very humid/hot days. I have set the code at any rpm, in hot and cool weather.

my friends scanner pull this misfire history:

Cyl

1. -13,422

2. -13

3. -11

4. -25

5. -39,363

6. -5,946

7. -9

8. -54,225

 

That's a pretty wide spread of misfires. Every cylinder has missed!

Upon resetting the code, it could go 1-4 days without setting it again, the longest between codes is 6 days, which came after treating the fuel tank with seafoam and injector cleaner, and also allowed seafoam to be injested through the throttle body to try and clean any carbon that may have built up over time. I have also cleaned the MAF and the air filter is new (5k ago).

I have checked for intake air leaks (hot and cold) and cannot find any at all, doesn't seem to have any exhaust leaks that i can hear clearly, maybe a little raspy like all my other 6l's.

Where should i go next? the symptons would indicate a air leak to me? Could I be missing an intake leak?

[gbayfisher]

Nobody yet?

An update to my problem>

I had reset the codes and waited for it to set again and it did. Freeze frame info is:

 

1.-2360

2.-4

3.-2

4.-9

5.-5463

6.-742

7.-1

8.-6261

 

Mileage since first failure 160kms

Mileage since mil request 120kms

 

 

Under freeze frame data:

-set code at 99 kms/hr after 16 minutes running

-set again at 117 kms/hr after 14 minutes of running

 

So it seems to set once up to running temps, I will wait to see what it tells me when it trips again. I don't know if this would be caused by an air leak? I am thinking not at this point, could be bad fuel or dirty injectors/contaminated rails?

I use 89 octane, with upto 10% ethonal I think, I will let this tank run empty and fill it up with 93 octane to see what it does. Also going to pull a few plugs to see if I can read them.

[59ih340]

Crank relearn.

[gbayfisher]

I am trying that this afternoon!

Hopefully my friend's snap on tool can do it .

 

Thx

[hockeypro1411]

This is a common problem with the 6.0's. My '03 does it all the time when it's held at 2500+ RPM's for 15-20 seconds or more. There's a few other people on here with the same issue. For some, the crank relearn works, for others (including me) it does nothing. I've tried everything that could possibly cause this and even some things that couldn't and the truck still does it. I can't feel and kind of miss or hesitation when the light starts blinking so I just ignore it.

[gbayfisher]

This is a common problem with the 6.0's. My '03 does it all the time when it's held at 2500+ RPM's for 15-20 seconds or more. There's a few other people on here with the same issue. For some, the crank relearn works, for others (including me) it does nothing. I've tried everything that could possibly cause this and even some things that couldn't and the truck still does it. I can't feel and kind of miss or hesitation when the light starts blinking so I just ignore it.

 

That's where mine seems to throw the codes, between 2200-2600, very light to almost no throttle and on down hill coasts when feathering the throttle. We just checked the injector rails and looked at the injectors, rails and everything else were absolutely spotless so we switched some injectors around to see if the freeze frame changes next time its shoots a code.

[hockeypro1411]

This is a common problem with the 6.0's. My '03 does it all the time when it's held at 2500+ RPM's for 15-20 seconds or more. There's a few other people on here with the same issue. For some, the crank relearn works, for others (including me) it does nothing. I've tried everything that could possibly cause this and even some things that couldn't and the truck still does it. I can't feel and kind of miss or hesitation when the light starts blinking so I just ignore it.

 

That's where mine seems to throw the codes, between 2200-2600, very light to almost no throttle and on down hill coasts when feathering the throttle. We just checked the injector rails and looked at the injectors, rails and everything else were absolutely spotless so we switched some injectors around to see if the freeze frame changes next time its shoots a code.

 

 

Yea if you look around here you'll find some more threads about this. As far as I know, nobody has found a solution. The worst part is that I don't feel any sort of miss or hesitation at all. I've got the light to come on and then went WOT and there was no sort of hesitation at all.

[gbayfisher]

This is a common problem with the 6.0's. My '03 does it all the time when it's held at 2500+ RPM's for 15-20 seconds or more. There's a few other people on here with the same issue. For some, the crank relearn works, for others (including me) it does nothing. I've tried everything that could possibly cause this and even some things that couldn't and the truck still does it. I can't feel and kind of miss or hesitation when the light starts blinking so I just ignore it.

 

That's where mine seems to throw the codes, between 2200-2600, very light to almost no throttle and on down hill coasts when feathering the throttle. We just checked the injector rails and looked at the injectors, rails and everything else were absolutely spotless so we switched some injectors around to see if the freeze frame changes next time its shoots a code.

 

 

Yea if you look around here you'll find some more threads about this. As far as I know, nobody has found a solution. The worst part is that I don't feel any sort of miss or hesitation at all. I've got the light to come on and then went WOT and there was no sort of hesitation at all.

 

 

 

Silly really! I hate seeing the light all the time. I wonder if those with a tune noticed any better results. Got some more digging to do and will see what comes up.

[gbayfisher]

Update.

 

So far could not find any issues with anything on the truck so i decided to do a crank relearn. So far so good!

Took the truck through the same road conditions that would normally set the code, and no codes!

 

I would hate to bring an issue like this to the dealer, you would lose your shirt paying for their handy guess work.

[jkellet1]

At the shop I work at we have had some luck with taking off the fuel rail and cleaning the injector screens and flushing the fuel rail itself well. We think the way the motor sits at an angle the gunk sits to the back and randomly floats up to the injectors. It normally works well.

[gbayfisher]

At the shop I work at we have had some luck with taking off the fuel rail and cleaning the injector screens and flushing the fuel rail itself well. We think the way the motor sits at an angle the gunk sits to the back and randomly floats up to the injectors. It normally works well.

 

 

 

We looked at that also, clean as whistle. Crank relearn fixed it for me, its been at least 3 weeks and no code again. Would have set buy now if it wasn't the problem.

[scott28641]

We replace the belt. Had 2 at the dealer this week and that fixed them both. The belt slips at a higher rpm throwing the crank sensor out of whack

[[email protected]]

We replace the belt. Had 2 at the dealer this week and that fixed them both. The belt slips at a higher rpm throwing the crank sensor out of whack

 

 

Do what? How in the hell can the belt slip and throw the crank sensor out of whack.

[scott28641]

We replace the belt. Had 2 at the dealer this week and that fixed them both. The belt slips at a higher rpm throwing the crank sensor out of whack

 

 

Do what? How in the hell can the belt slip and throw the crank sensor out of whack.

 

 

I don't know, I only write up the ro's. I'll ask the tech monday.

[wthor]

I have been told that the crank relearn procedure is only done on motors with a distributor. My 04 2500HD 6.0L has a coil for each spark plug. I have a misfire code only above 68 MPH (flashing cel) if I slowdown back to 62 MPH the misfire clears (no flashing cel).

My question is can a crank sensor relearn be conducted with the Snap-on analyzer on my truck?