Code question

[JoeyNigs]

Check engine light steady on. Gas cap fine. Pulled up codes in 10 PCM..getting PO 300 H..I know PO 300 is Engine misfire detected, what does the " H " stand for in PO 300 H ? Thanks

 

[82shark]

H is usually a History code.
ed

 

[Bioscache2]

The H means, as pointed out above, a history code. This means the engine has run within the acceptable paramters enough times for the engine to label the problem as no longer current. How many times the engine has to run well is different for each code though so I don' know if its something you need to worry about.