A flashing check engine light means the engine computer has detected a misfire severe enough to damage the catalytic converter. Unburned fuel from the misfiring cylinder enters the exhaust and can overheat the converter. Reduce speed and load, avoid hard acceleration and get it diagnosed as soon as possible. A solid light means a fault has been stored but is less urgent.
Flashing vs solid check engine light
| Light | Meaning | What to do |
|---|---|---|
| Flashing | Active severe misfire | Ease off, avoid heavy load, diagnose immediately |
| Solid | Stored fault such as a sensor, leak or emissions issue | Scan the code soon; see check engine light |
Flashing and the car is shaking
Shaking with a flashing light is the misfire itself: one or more cylinders are not firing. Common causes are a failed ignition coil, a worn or fouled spark plug, a leaking or stuck injector, a vacuum leak at one cylinder, or low compression; see ignition coil symptoms, spark plug symptoms and low compression in one cylinder.
Flashing when accelerating, then it stops
A light that flashes only under acceleration and then returns to solid or goes out points to a misfire that only happens under load, often a weak coil or a plug gap that has grown with wear. The code is usually stored, so a scan tool can read which cylinder misfired.
Flashing with the traction control light on
Many vehicles disable traction or stability control when they detect a misfire, because those systems rely on predictable engine torque. The traction light usually goes off once the misfire is repaired and the codes are cleared.
What the codes tell you
- P0300: random or multiple cylinder misfire
- P0301 to P0308: misfire on a specific cylinder
- Lean codes such as P0171 alongside a misfire suggest a vacuum leak or fuel delivery problem
Quick diagnosis
- Read the codes; see how to use an OBD2 scanner.
- For a single cylinder, swap that coil with a neighboring cylinder and see whether the misfire moves.
- Inspect the plug from the misfiring cylinder.
- If the misfire stays with the cylinder, run a compression test; see compression and leak-down tests.
Can you keep driving?
Drive only as far as needed, gently. Continued driving with a flashing light can ruin the catalytic converter and wash oil from the cylinder walls. If the misfire comes from internal engine damage, see engine misfire and compare repair costs with our replacement engines.
Trouble codes: P0302 cylinder 2 misfire · P0303 cylinder 3 misfire · P0304 cylinder 4 misfire · P0305 cylinder 5 misfire · P0306 cylinder 6 misfire · P0307 cylinder 7 misfire · all OBD2 codes.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.