03 6mt Coupe here.. So I normally drive my car locally in the streets and decided to take a 3 hour trip out to Massachusetts the other day from NYC. About 1 mile into the drive, my Service Engine Soon light comes on, but my car feels totally normal. I scan the car using the OBD ii machine and it give me two codes: both P0300, except the second one says (PENDING).

I make the drive there and back, and 2 days later after getting back, I start my car one day and my SES Light is gone? I know its a random misfire, so i am not sure what happened and why the light is gone?

I used the OBD ii scanner again even though the light is gone, and it still reads me the code, but this time only one p0300 code, the pending one is gone.

Any idea what I should do? Has this ever happened to anyone?

 

Basically your engine lost spark for a couple cycles, probably under either high load or very high rpm, the ECM detected it and there was enough missed cycles to trigger the 2-trip detection and light up the CEL (requires 2 separate detections to trigger the CEL). The PENDING code is a single trip detection during one drive cycle.

Usual suspects are worn sparkplugs, or oil pooling in the spark plug well tube, rarely a damaged coil pack and the damage is typically visible, either a scorched well tube boot, or corroded contact spring inside the boot, or blistered/swollen epoxy resin encapsulation (black shiny part on the top).

Pull out your plugs and you will almost definitely find the issue somewhere along the process.

 

So i def. still have to get this checked out even though the light isnt on anymore?

 

Yep, it came on for a reason.