0300 while driving today

[03yukXL]

Hey all,

Thought I had this old bird ironed out. Got about 60 miles into a 5 hour drive today and of course it chooses today to throw the p0300 error. No stored code. Running though, shifting hard. I have read things talking about crankshaft position sensors, camshaft senosors as well as a convincing video about a ground on the drivers side toward the bottom of the block. The immediacy by which it came on is weird. Isn’t intermittent either it seems. Shut it down a couple of times and it didn’t seem to help. Any thoughts?

 

[Fless]

Connect a scanner that can count up the individual cylinder misfires to see if you can tell which one might be causing the code.

Does the P0300 go away with an ignition cycle?

 

[Scottydoggs]

if the cel is flashing the cats might be clogged up. that can cause a p0300 code and make it feel gutless.

 

[03yukXL]

Connect a scanner that can count up the individual cylinder misfires to see if you can tell which one might be causing the code.

Does the P0300 go away with an ignition cycle?

It didn’t but I only cycled it a couple of times. I don’t think it is the cats because it has had decent power and it came on suddenly. I can tell it stumbles when i rev it at a stop too. Really seems electrical in nature …

 

[Scottydoggs]

if you've not had a tune up done in some time that might be all it needs. (plugs and wires) if you can get a scanner that shows live data then you can see what plug is misfiring, or if its most of em. p0300 means more then one misfire. p0300 = multiple random misfires.

if the cel does not stay lit up on a re start the p0300 code will clear its self on a re start as its only a pending code till a hard cel is lit up full time.

 

[Fless]

Just to rule it out, do a crankshaft correlation procedure with an advanced scan tool.

Any recent work done to it, any sensors changed, etc.?

 

[rockola1971]

When the CEL is flashing at you (Didnt see you answer one of the guys that asked if it was flashing at you in post#3) this typical means the engine is experiencing misfires. Could be legit or could be caused by a host of things including the knock sensors and their wiring harness.
First thing I would check is misfire counts on live data. A bad spark plug its wire or coil will show its ugly head and stand right out. Just have to determine which one for any given cylinder is at fault.

Where GM let us down is there are certain conditions and timeframes that have to be met to set a code, cause a code to pop up(Show CEL) for all the various codes that are possible. Many can and are intertwined because of things as basic as certain sensors are powered by the same reference voltage. They failed us by trying to keep things cheap. They could have done a better job with the PCM system.

 

[MassHoe04]

Less time for software engineers to program, if you lump a bunch of random things into one generic code...
Always about the bottom line!

Also, means potentially more returns to the dealer's service department if a code is difficult to fully and completely diagnose.
$$$

 

[03yukXL]

Well I ended up dropping it at a mechanic because I was actuall driving it on a work trip 250 miles away when it went bad on me. Couldn’t have had an issue the 100 times I was driving it within limping distance of home! Anyway, the mechanic called today and said he thinks it needs intake manifold seals because it is reading lean and corrects itself with some spray around the runners. We will see!

 

[rockola1971]

Less time for software engineers to program, if you lump a bunch of random things into one generic code...
Always about the bottom line!

Also, means potentially more returns to the dealer's service department if a code is difficult to fully and completely diagnose.
$$$

They could have added some more voltage/current pickoff points and I/O in the PCM to where it could actually tell you what exactly is wrong. But you are right, its that bottom line and adding $50 worth of wire and labor to a car/truck during production times all of the vehicles produced adds up REAL fast....into millions of dollars.