P0300: Something else to look for.

[08H3]

I had an intermittent P0300 that would come and go, infrequently. Between the first and second time was about 3 months, then the second and third about a month, then a couple weeks. That code gives no information by itself, but I pinned my hopes that it was the plugs since I am creeping very near to 100K. I decided to change them just because that was the easiest possible fix, and in the process found the true cause. Two of the coils had rubbed against the engine and rubbed the insulation off the wires. There were very clear marks where it had been arcing. I'm really not sure what the correct fix for this is, but I carefully taped up each wire and then put it in a wire loom where it had been abraded.

I don't recall this ever being brought up as a possible cause, and I never would have caught it other than 50% luck and 50% attention to detail. Maybe this will help someone else tracking down this electrical gremlin.

Note: I do have pics of this if anyone needs them, but it should be clear.

 

[alrock]

Thanks for this find. There are so many possible causes for the P0300 and now we have another way to narrow it down.

 

[Kurteken]

Hi,

thank you for writing this down. There are several causes for a P300 and in the morning i will look (is now 5 am) if this is happening with my H3. My engine check light is on all the time. I've checked almost everything. Friends tell me my light is on because i drive on liquid gas.
I check my wires and let you know.

K.