Check engine light flashing

The short answer

A steady light means "get it checked". A flashing light means "this is happening right now". The US OBD rules say the light blinks once per second while a misfire that can damage the catalytic converter is going on (CARB 13 CCR 1968.2, which the federal rule adopts in 40 CFR 86.1806-17). Unburned fuel goes into the hot exhaust and burns inside the converter. That can overheat it within one drive. A catalytic converter was the number 1 check engine repair in CarMD's 2025 data, at an average of $1,511 (CarMD 2026). RepairPal puts a replacement at $2,280 to $2,480 (RepairPal, updated September 3, 2026). Most misfires are fixed with a spark plug or a coil for a few hundred dollars.

What to do now, in order

1. Ease off. Slow down, avoid hard acceleration, hills and high speed. GM's owner's manual says to "reduce vehicle speed and avoid hard accelerations and uphill grades" (2022 GMC Acadia manual).
2. Do not tow or carry heavy loads. If you tow a trailer, drop the load as soon as you can. The EPA says not to drive "at high speed or with excess weight (such as towing or carrying heavy equipment)" (EPA).
3. Pull over if it gets worse. If the car shakes hard, loses power, or you smell fuel or burning, pull over when it is safe and switch off. AAA says to pull over and shut off the engine when the light flashes and the car drives badly or you notice smoke or strange smells (AAA).
4. Park away from anything that burns. The exhaust can be very hot. Ford's manual warns that misfire can overheat the exhaust and damage "interior floor coverings or other vehicle components, possibly causing a fire" (Ford owner's guide). Honda tells owners to park "in a safe place with no flammable items" (Honda owner's manual).
5. Let it cool, then restart once. Honda says to wait at least 10 minutes with the engine off. If the light blinks again after a restart, drive to a dealer at 31 mph or less. GM says to wait at least 10 seconds before restarting and to see a dealer as soon as possible if it still flashes.
6. Read the codes. An OBD2 scanner shows which cylinders misfire, which often points straight at the part (see below).
7. Fix it before you drive far. Every mile with a flashing light puts the converter at risk.

Is it safe to drive with a flashing check engine light?

Only a short, gentle distance, to get somewhere safe or to a shop. The EPA says you "can still drive safely, but should minimize your time on the road". Consumer Reports says to reduce speed and the load on the engine (Consumer Reports). Stop driving at once if:

• the engine shakes hard or loses a lot of power,
• you smell raw fuel or something burning,
• you see smoke,
• the temperature gauge climbs or other warning lights come on.

If none of that happens and the light goes back to steady, the misfire has stopped for now. It is still worth fixing within days, because it will come back.

Why the light flashes, then stops, then stays on

The rules let the light stop blinking when the misfire stops, but it stays lit because the fault is still stored. The same rules let the light go out after three drives in similar conditions with no misfire (CARB 13 CCR 1968.2, section (e)(3.4)). That explains the patterns people search for:

• Flashing, then stops: the misfire comes and goes, often with load or engine temperature.
• Flashing, then stays on: the misfire stopped, the code is stored.
• Flashing when accelerating: the misfire happens under load, which points to spark: a worn plug or a weak coil that breaks down under high cylinder pressure.
• Flashing and car shaking: you can feel the missing cylinders. This is the most urgent version.

Some cars do not blink at all. The rule lets a car keep the light steady if it cuts fuel to the misfiring cylinder instead. So a steady light with a strong shake deserves the same care.

The likely causes

Almost every flashing light is a misfire. These are the common causes, most likely first:

Some engines have a known problem with a manufacturer bulletin or a longer warranty. Our P0300 page lists them with links: for example the Chrysler 3.6L V6 cylinder head extension (10 years or 150,000 miles), coolant getting into cylinders on the Ford 1.5L EcoBoost, GM active fuel management lifters, and the 2008-2012 Honda Accord V6. Check your car against them before you pay for an engine repair.

What an OBD2 scanner shows

A scanner turns "it is flashing" into "cylinder 3 is missing under load".

• The code. P0300 means several cylinders or no single one. P0301 to P0308 name the cylinder: P0301 is cylinder 1, P0302 is cylinder 2, and so on. A lean code (P0171, P0174) or a cam timing code (P0016) with it points to the cause.
• Pending codes. The rules store a pending code before the light blinks, so read pending codes as well as stored ones.
• The freeze frame. A snapshot of rpm, load, speed and coolant temperature when the fault was recorded. Idle points toward leaks and injectors; high load points toward plugs and coils.
• Misfire counts per cylinder (Mode 06). On CAN cars from the 2005 model year, the engine computer must report misfire test results in the standard format (CARB 1968.2 (g)(4.5.4)). Monitor A1 is all cylinders; A2 is cylinder 1, A3 cylinder 2, and so on. Counts spread over every cylinder point to a shared cause. One cylinder far ahead of the rest points to its plug, coil or injector.
• Live data. Rpm dipping in a rhythm at idle, short-term fuel trim jumping as unburned oxygen reaches the front oxygen sensor, and long-term fuel trim far from 0% if the mixture is lean.

What healthy looks like: on our own 2010 Honda Accord, the Mode 06 misfire counts from the last drive read 0 on cylinders 2, 3 and 4 on every scan from August 14 to September 24, 2026, and 0 to 3 on cylinder 1. We have not recorded a car with a flashing light yet, so we show no chart here. When a misfire is bad enough to flash the light, the counts on the affected cylinders climb far above that.

What it costs

National averages for the full job at a shop, parts and labor, from RepairPal (updated September 3, 2026):

CarMD's 2026 report, from more than 39 million vehicles, ranks ignition coil and spark plugs together as the number 3 check engine repair ($480), an ignition coil alone number 5 ($256) and spark plugs alone number 10 ($299). The average check engine repair in 2025 was $554. CarMD's averages come from a different method, so they sit below RepairPal's shop estimates. The lesson from both: fixing the misfire early is cheap, and the converter is the expensive part you protect by slowing down.

When is it safe again?

After the repair, clear the code and drive normally. The misfire monitor runs all the time, so a real misfire usually shows up again within one or two drives. Check the per-cylinder counts after the first drive: they should be at or near 0. If you drove a long way with the light flashing, ask the shop to check the converter too, because a damaged converter can set P0420 later.

Questions people ask

Can I drive my car with the check engine light blinking?

Only gently and only as far as you must. Slow down, avoid towing and hills, and stop if the car shakes hard or you smell fuel or burning.

What is the most common cause of a flashing check engine light?

An engine misfire, most often from worn spark plugs or a failing ignition coil.

Which is worse, a blinking or a solid check engine light?

Blinking. A solid light means a fault was found. A blinking light means a misfire bad enough to damage the catalytic converter is happening right now.

How do I fix a flashing check engine light?

Read the codes and the misfire counts, then fix the cause: usually plugs or a coil. Clearing the code does not fix anything; the light comes back if the misfire does.

Why did the light flash and then stop?

The misfire stopped for the moment. The rules let the light stop blinking when the misfire stops, but it stays on while the fault is stored.

Why is my traction control light on with a flashing check engine light?

Some cars switch off traction or stability control when the engine has a fault and show that light too. Your owner's manual says whether yours does. Fix the misfire first.

My check engine light flashes for a few seconds when I turn the key, then goes out. Is that a misfire?

Probably not. A misfire can only happen with the engine running. Some cars use the light at key-on to show that the emissions self-tests have not finished. Your owner's manual explains what yours does. If it flashes with the engine running, treat it as a misfire.

Will a flashing check engine light fail an emissions test?

Yes, while the light is on. Texas, for example, fails a car when the light is commanded on with a code set (Texas DPS).

Misfire codes

• P0300: Random or multiple cylinder misfire
• P0301: Cylinder 1 misfire
• P0302: Cylinder 2 misfire (no guide yet)
• P0303: Cylinder 3 misfire
• P0304 to P0308: Cylinders 4 to 8 (no guide yet)
• Related: P0420 catalytic converter, P0171 lean bank 1, P0174 lean bank 2, P0016 cam and crank timing

Sources

• California Air Resources Board, 13 CCR 1968.2 OBD II Final Regulation Order (2015) ww2.arb.ca.gov
• California Air Resources Board, 13 CCR 1968.2 (2006 order, Mode 06 misfire results on CAN vehicles) ww2.arb.ca.gov
• 40 CFR 86.1806-17 (federal adoption of California OBD rules), Cornell LII law.cornell.edu
• US EPA consumer brochure EPA420-F-02-016 (2002, archived copy) 19january2021snapshot.epa.gov
• California Air Resources Board OBD II fact sheet ww2.arb.ca.gov
• Honda owner's manual (2025 Pilot), malfunction indicator lamp techinfo.honda.com
• Ford 2012 Super Duty owner's guide fordservicecontent.com
• GM 2022 GMC Acadia owner's manual gmc.com
• AAA, check engine light aaa.com
• Consumer Reports, what the check engine light means (updated March 1, 2026) consumerreports.org
• CarMD 2026 Vehicle Health Index press release (April 22, 2026) prnewswire.com
• RepairPal estimator pages (updated September 3, 2026), linked in the cost table.
• Texas DPS emissions testing FAQ dps.texas.gov