The short answer
A flashing check engine light means the engine is misfiring badly enough to dump unburned fuel into the exhaust, which can wreck the catalytic converter within minutes. Pull over, shut it off and have it towed or driven very gently to a shop. A solid light means a fault has been stored; it is safe to drive carefully, but have it diagnosed soon.
Flashing: stop
The engine computer flashes the light only for one reason: a misfire severe enough to damage the catalytic converter. Raw fuel burning inside the converter overheats it in minutes, and a converter is one of the most expensive single parts on a modern car. If the light flashes, especially with shaking, loss of power or a smell of fuel, pull over as soon as it is safe, shut the engine off, and get the car to a shop without driving it hard. A tow is cheaper than a converter.
Solid: diagnose soon
A steady light means the computer has stored a fault code. It could be as simple as a loose gas cap or an aging oxygen sensor, or the early stage of something bigger. The car is usually safe to drive normally, but the longer you leave it the more likely a cheap fix becomes an expensive one, and in Manitoba an illuminated check engine light can also affect a safety inspection. Book a diagnostic within the week.
Flashing then stops, or flashing in the cold
A light that flashes for a few seconds and then goes steady recorded a misfire that has calmed down. The code is still stored and the cause is still there. Cold Winnipeg mornings bring out weak ignition coils, tired spark plugs and injectors, so a misfire that only appears at −25°C is still a misfire. Mention the conditions when you book; it helps the diagnosis.
Why a free code read is not a diagnosis
Parts stores will read the code for free, and the code is useful, but it names the symptom, not the cause. A P0300 random misfire code can be plugs, coils, injectors, a vacuum leak, low compression or a fuel pump. Replacing parts in code order is the expensive way to find out. A proper diagnostic uses live data, tests the suspected part and confirms the fault before quoting the repair. That is what you pay a diagnostic fee for.
What to tell the shop
- Flashing or solid, and when it started.
- Any change in how the car runs: rough idle, hesitation, poor fuel economy, smells.
- Recent work: fuel-ups, repairs, modifications, a new tune.
- Whether anyone has cleared the code already.
Garage 46 diagnoses the actual fault first, explains it in plain language and quotes the fix before any work. On tuned and modified cars we also check whether the calibration is part of the problem.