A blinking Check Engine, not a steady one: the difference
A steady lamp means «look into it soon». A blinking one means «stop». Two different messages, and the difference is expensive.
There is one lamp on the dashboard, but it carries two different messages, and mixing them up is expensive.
Steady
The unit found a fault and stored a code. You can drive: home, to work, to a garage. The car may run in a protective mode and drink more than usual, but nothing is being destroyed right now.
Blinking
Misfires are happening, and unburnt fuel is going into the exhaust. There it burns — inside the catalytic converter, which was not built for it. The honeycomb melts within tens of kilometres, and a new catalyst costs about half an engine rebuild.
So a blinking lamp does not mean «hurry up», it means «stop driving»:
- Reduce the load: off the throttle, keep the revs down.
- Pull over and switch the engine off.
- Start it again and see whether it still blinks. If it does, continue only on a tow truck — or very gently and slowly if the garage is a kilometre away.
Why misfires happen
The causes are the same as for P0300 and its relatives: plugs, a coil, an injector, bad fuel, an air leak. Blinking differs not in cause but in quantity: the unit counts the misfires and starts blinking when the count crosses the threshold at which the catalyst suffers.
What to look at once you have stopped
Plug in an adapter and look at the misfire counters per cylinder. One counter ticking means that cylinder. Several ticking means a common cause — do not replace the plugs one by one.
What not to do
- Clear the code and drive on. The lamp goes out, the misfires stay, and the catalyst keeps burning.
- Replace the catalyst first. While the cause is still there, the new one dies the same way.
- Wait for it to pass. Misfires do not pass by themselves.
