need help asap code p0300
#2
#3
TECH Fanatic
Join Date: Jun 2008
Location: Dallas, TX
Posts: 1,174
Likes: 0
Received 0 Likes
on
0 Posts
I had this code and it turned out to be a spun rod bearing. Once it got to the point that the CEL would flash, we started digging into the bottom half and found the issue.
I hope yours is something simple. How old are the spark plugs and wires? Do you have a cam or any power adders?
I hope yours is something simple. How old are the spark plugs and wires? Do you have a cam or any power adders?
#7
Launching!
Thread Starter
Join Date: Jun 2011
Location: Lewes DE
Posts: 211
Likes: 0
Received 0 Likes
on
0 Posts
My friends uncle races vettes so he took all brand new coils wires plugs and still misfired on cylinders 4,6,8 he thinks its a bad o2 sensor but ill know today
Trending Topics
#12
I see them all the time, just more on the 5.3 & 6.0l truck engines. The o2 shorts internally, and causes it to be fat as ****, kills the plugs, then you can figure it out from there.
#13
I'm having an issue like this too.
I was at Gingerman a week ago Sat. Had the random misfire code followed by a bank 1 lean code. Reset the codes and saw the bank 1 lean code come back on Sunday. Then again on the ride home. Reset again and the bank 1 lean code came on again last week. Going for new plugs this weekend. What is the best way to test the o2 sensor? Or should I just change it?
TIA
I was at Gingerman a week ago Sat. Had the random misfire code followed by a bank 1 lean code. Reset the codes and saw the bank 1 lean code come back on Sunday. Then again on the ride home. Reset again and the bank 1 lean code came on again last week. Going for new plugs this weekend. What is the best way to test the o2 sensor? Or should I just change it?
TIA
#14
TECH Fanatic
Yes! Although it will also cause rich, high voltage, low voltage, circuit performance, and cross count DTC's as well.
Unlikely. I have seen Long Term fuel trims at -100 and it still did not cause a miss. A vacuum leak is usually the only thing that will cause a lean misfire unless the fuel injector data is way off in the tune.
Shorted - an abbreviated term to indicate that an electrical circuit is traveling along an unintended path.
Shorts to what? Voltage? Ground? The median 02 sensor voltage is .450v, if it stays over or under this baseline value for too long it will set a crosscount DTC (this sets if the 02 sens. voltage does not cross this .450 threshold a specified number of times within a set duration) and will be disregarded. The 02 sensor itself generates electricity based upon the difference in oxygen content between the atmosphere and the exhaust.
The PCM averages the AFR by crossing the .450v threshold which translates into rich/lean. The sensors can get poisoned, read lazy (shooting way over like .820v then to .270v rather than staying closer to the .450 baseline), or just be dead...although most times it is indicative of another problem that has manifested (ie., vacuum leak, leaking injector, worn valve seals/guides, etc).
It would take a lot of fuel to cause a miss (enough to smell and know there was a problem), and I wouldn't think there would be that much adjustability in the fuel trims alone to allow that much fueling unless the tune had been altered. I guess if there was a rich condition for long enough (caused by a leaking injector, regulator, etc) the sensor could get poisoned and read lean over time, inducing the higher fuel trims in addition to the unmetered fuel, but that's what I would be looking for.
Maybe you're speaking in vague generalized terms when you say "shorted", although it is not actually shorted. Many people say something is "shorted" to mean its fucked up when it's not really "shorted" to anything. It really bothers the **** out of me when people describe something as "shorted" when its actually open. It's a peeve of mine.
There are different types of "miss fire's", they manifest themselves under different conditions and feel different. An ignition miss will be much more pronounced under a heavy load than that of a lean miss...something you have to get a feel for over time.
I posted to a thread a while back about diagnosing a miss and what to look for...I'll try to find that and link it here.
Edit: Here it is....https://ls1tech.com/forums/generatio...ion-issue.html
Shorts to what? Voltage? Ground? The median 02 sensor voltage is .450v, if it stays over or under this baseline value for too long it will set a crosscount DTC (this sets if the 02 sens. voltage does not cross this .450 threshold a specified number of times within a set duration) and will be disregarded. The 02 sensor itself generates electricity based upon the difference in oxygen content between the atmosphere and the exhaust.
The PCM averages the AFR by crossing the .450v threshold which translates into rich/lean. The sensors can get poisoned, read lazy (shooting way over like .820v then to .270v rather than staying closer to the .450 baseline), or just be dead...although most times it is indicative of another problem that has manifested (ie., vacuum leak, leaking injector, worn valve seals/guides, etc).
It would take a lot of fuel to cause a miss (enough to smell and know there was a problem), and I wouldn't think there would be that much adjustability in the fuel trims alone to allow that much fueling unless the tune had been altered. I guess if there was a rich condition for long enough (caused by a leaking injector, regulator, etc) the sensor could get poisoned and read lean over time, inducing the higher fuel trims in addition to the unmetered fuel, but that's what I would be looking for.
Maybe you're speaking in vague generalized terms when you say "shorted", although it is not actually shorted. Many people say something is "shorted" to mean its fucked up when it's not really "shorted" to anything. It really bothers the **** out of me when people describe something as "shorted" when its actually open. It's a peeve of mine.
I'm having an issue like this too.
I was at Gingerman a week ago Sat. Had the random misfire code followed by a bank 1 lean code. Reset the codes and saw the bank 1 lean code come back on Sunday. Then again on the ride home. Reset again and the bank 1 lean code came on again last week. Going for new plugs this weekend. What is the best way to test the o2 sensor? Or should I just change it?
TIA
I was at Gingerman a week ago Sat. Had the random misfire code followed by a bank 1 lean code. Reset the codes and saw the bank 1 lean code come back on Sunday. Then again on the ride home. Reset again and the bank 1 lean code came on again last week. Going for new plugs this weekend. What is the best way to test the o2 sensor? Or should I just change it?
TIA
I posted to a thread a while back about diagnosing a miss and what to look for...I'll try to find that and link it here.
Edit: Here it is....https://ls1tech.com/forums/generatio...ion-issue.html
Last edited by DMM; 05-01-2012 at 10:17 PM.
#18
TECH Fanatic
iTrader: (5)
When I put in a new ECU it gave an intermittent P0300 with no driveability issues. Doing the CKP crank relearn solved it. Dealer tech said it would not fix it... that there's a code just for that... but it has to be way off to get that code... don't always listen to dealers no matter how cocky they sound. Had an independent place do it with the Snap On scanner