Just after a bit of advice. I own a MK1 2001 (Y Plate) ford focus hatchback 1.4. I was recently having a problem with the cars performace due to a misfire on pot 2. I changed the plugs, leads and coil, the car now runs like new, no complaints, however the engine warning light is still on. I disconnected the earth from the battery for 30 mins to reset the car and the light went out. This morning i switched the car on and the light is back. Any idea's what i can check how to check it.