Hello
Week ago when i driving on highway (5th gear, 80mph) my car (WRX 2005) lose power and P0303 error code popup. That same issie i have around 2 ys ago but i stop and reset ECU and was fine, now is permanently. The 1st i think about coul pack because this is tipical when i search forums, and YT. Subaru service manual said P0300 (1,2,3,4) should focus on injector and injector circuit. But in my example looks like injector working , coil pack working because when i start engine i feel engine shaking and also i smel petrol from surround cylinder 3, so i can said injector working fine, coil OK because i testing on other cylinder but looks like wiring problem ?? or ECU ?? how i can test , mesure wires supply coils ?? because i think the problem is there somewhere .

Thanks

 

Have you swapped 2 coils over to see if the problem moves from cylinder 3 to a different cylinder with the coil pack? This will prove either coil pack or wiring at fault on cylinder 3.

 

I had a similar code a couple of years ago. Switched the coil packs, and the code stayed the same, so it wasn't the coil pack. Changed the plug and it went away - in the end I just replaced all the plugs with new ones. Doubt it had had new plugs since new! No issues since (touch wood)