As stated, on solid means it has stored a code. You need a reader to access the PCM to retrieve the code. Hope you never have a flashing check engine light. That is a very bad thing., indicating a misfire. This flashing check engine light means you are doing “mechanical damage” to your vehicle if you continue to drive under these conditions. If you see a flashing check engine light you should seek immediate professional advice. By mechanical damage I am talking about things like the catalytic converter, the exhaust manifold, pistons, rings, valves – virtually all upwards of four-digit repair bills.