P0300 - Random/Multiple Cylinder Misfire Detected.
P0420 - Catalyst System Efficiency Below Threshold (Bank 1).
P0440 - Evaporative Emission Control System Malfunction.
The type of ignition system and specific parts depends on which engine you have. You did not list that.
The flashing Check Engine light indicates the most serious of conditions, and you are supposed to stop the engine right away. Too much unburned fuel is going into the exhaust system where it will burn in the catalytic converter and damage it. Code 420 indicates this may have happened already. The first thing to address is the code 300. That could indeed be caused by a weak ignition coil, but based on the mileage, an equally-good suspect is worn spark plugs and wires. You might want to start with a general tune-up, erase the fault codes, then see which ones set again. Code 300 with the flashing Check Engine light suggests the misfires are spark-related, not fuel-related.
Feb 19, 2017 at 10:48 AM
