You're cruising along when for a reason, the dashboard suddenly calls you attention. That check engine signal light isn't just illuminated, it's flas
You’re cruising along when for a reason, the dashboard suddenly calls you attention. That check engine signal light isn’t just illuminated, it’s flashing. Mentioning perhaps the vehicle starts shaking. It could be low acceleration, an inconsistent exhaust note or gasoline odor from the cabin.
Normally, a blinking check engine light is a lot different than a check engine light that stays on all the time. In most modern type of cars, it translates to a huge signal coming from the computer to alert of an active engine misfire that could cause damage to the catalytic converter. This could indicate improper combustion inside the engine, and fuel contamination of the exhaust.
It’s not a message to ignore until the next oil change. If the car continues to be driven it could lead to a more costly exhaust system problem and not a minor issue like a worn spark plug or worn ignition coil. The best thing to do is to slow down and cut load on the engine, stop and have a proper diagnosis.
Flashing Versus Solid Check Engine Light
A flashing check engine light often signals a problem in which one or more cylinders in the engine not only burn fuel properly, but actually complete combustion at all. Where the failure occurs is called a misfire. During a normal combustion cycle, an engine mixes in the air and fuel, then compresses and precisely times the ignition.
If there is a failure in that process, there is a risk that some fuel will not be consumed, or may escape partially combusted. It then passes through the exhaust system and into the catalytic converter which runs at very high temperatures. In trying to process the excess fuel, the converter can get hotter.
Warning techniques used by the different vehicle manufacturers may differ slightly; the owner’s manual should always be consulted. However, when the malfunction indicator light flashes, it usually means there is a serious problem, and that action needed to be taken instead of a maintenance schedule.
With this, it’s time to examine the differences between flashing and solid check engine light.
There is a difference between a solid and flashing check engine warning light.
If there is a fixed light, that implies that the computer in the vehicle has detected a malfunction in the engine, emissions or powertrain system. It could be a minor issue, like a slight problem in the evaporative-emissions system, or something more. The vehicle needs to be checked in the near future, but may be operating properly.
If the light is flashing, then it indicates that the fault is occurring actively and may be causing a rapid damage. The driver may experience other symptoms, such as subsequent shakes, hesitation, loss of power or unequal exhaust note simultaneously.
Warning: Do not ignore either warning. But the quicker response goes to the flashing version. Consider a steady light a ‘Schedule a diagnosis’ and a flashing light a ‘Stop stressing the engine and deal with this now’.
Why a Severe Misfire Can Damage the Catalytic Converter
The catalytic converter is located within the exhaust system and aids in converting harmful gases to less harmful emissions. It has an internal structure with a coating that provides performance in a specific temperature range.
In case of a serious misfire, the fuel may move through the cylinder without combustion. With that fuel entering the hot exhaust system it can start burning or cause excessive heat to build in the converter. The internal material may melt, crack or become restricted.
Unfortunately, if the converter is damaged, you will likely experience slow acceleration, higher emissions, some rattling sounds or extra warning lights. In severe cases, too much exhaust heat may leak to neighboring vehicle components.
That’s why it is so important that the flashing light happens. While the original may be caused by a small part in the ignition system which can be replaced, future driving can cause the second which may be expensive.
Most Common Causes of a Flashing Check Engine Light
There are many issues that can disrupt combustion and speculating is an expensive proposition. The most popular options are:
- Spark plugs that are fouled, worn or misgapped
- Failure of the ignition coils or weak ignition coils
- Burned out spark plug wires on vehicles that use them
- Dirty/g leaking fuel injectors or electrically problems with fuel injectors
- Low fuel pressure from a pump or fuel-delivery problem
- Intake or vacuum leaks that could cause insufficient or excessive mixture of air and fuel
- Wrong timing of valves and ignitions
- Caused by valve, piston or damage head gasket which causes low compression.
- Crank- or Camshaft positions wrong.
Most Common Causes of a Flashing Check Engine Light
While it’s a good thing that a loose gas cap can cause a continuous emissions warning message, it’s not the first possibility to exclude when the warning light is flashing while the car is running and the power level is poor.
Warning signs that often come with the flashinglight:
A flashing warning light is more often than not accompanied by other indicators or lights. This could cause the engine to be shaky at idle because one cylinder will no longer be working equally. The car may be slow to accelerate, surging or struggling to get faster.
Other symptoms are exhaust popping, a decrease in fuel efficiency, heavy fuel odor and significant loss of performance. It may appear not to have a problem at idle, but misfire when going uphill or accelerating to a highway speed. This may occur when a lesser ignition coil only fails under heavier load.
Pay attention to smoke, loud mechanical noises, overheating or an oil-pressure warning. Those symptoms can be symptoms of something other than a “normal” ignition misfire. If multiple warnings are concurrent, stop the vehicle’s engine as soon as the vehicle has been safely stopped.
If the light flashes, here are some steps to take:
Drive slowly and be cautious: do not rush or accelerate rapidly. Slow down, go downhill and head towards a safe parking spot. If required by traffic conditions, activate the flashing light signals (ambulance lights).
When stopped, listen for something and engage Park. If it’s subjected to severe shaking, knocking, smoke, overheating, a strong raw-fuel smell or very weak power, stop the engine immediately. Make arrangements for roadside assistance rather than attempting to use any power to get to a workshop.
Avoid starting and restarting the engine or revving it repeatedly to see if it clears up.” That will further perpetuate the conditions that can overheat the converter.
If it’s safe, you may check end a hose or electrical connector for an obvious disconnection. The visual inspection is not an alternative to diagnostic tests.
Failing to Fix a Flashing Check Engine Light
It is not recommended to continue along a normal journey. When the car is still running, this flashing warning indicates that some problem has been identified which is serious enough to require action.
Use the lowest throttle possible to get to a truly safe place if it starts flashing when you are in a risky location. Try not to drive at high engine speeds, too fast, towing, steep climbs and long drives.
Once clear, it is usually safer to have a tow. This might seem rather finesilly if a repair shop is just a few miles away, but there’s no definitive “stop” mileage for a misfire that will damage a catalytic convertor. The amount of damage is influenced by the degree of fault, load on the engine, exhaust temperature and the vehicle involved.
Getting towed is really annoying. Changing a converter and the underlying causes of the original missfire are typically worse.
How does a Mechanic know that the misfire is to blame?
Diagnostic is typically started after connecting the OBD-II scan tool to the vehicle and reading any stored diagnostic trouble codes and pending diagnostic codes. P0300 is for random or multiple cylinder misfires. Codes like P0301, P0302, P0303 indicate which one of the cylinders is the cylinder with the misfire that is detected by the computer.
This code refers to the system or cylinder that is being affected by the problem, not the part that is faulty. For instance, if P0302 is present it does not necessarily mean that spark plug #2 is bad. It could be due to the fact that it has a coil or injector, wiring, compression or an air leak somewhere in that part of the engine.
A technician can check misfire counts, fuel trim readings, ignition parts, and injector function as well as the engine compression. Another way to determine if the misfire moves with the cylinder is to swap out the coil that may be suspect.
Before replacing parts, there is good diagnosis. If no, the repair can cost an exorbitant amount of money and a ton of guesswork.
What If the Flashing Light Stops by Itself?
If there is no flash, that does not mean the problem has gone away! The misfire can only happen at idle, at a certain engine speed, in bad weather or under hard acceleration. After the warning is changed and no longer appears on the computer, pending or stored codes may still be present.
Do not delete those codes or disconnect the battery prior to diagnosis. Non-volatile memory, and freeze frame data provide the technician with some idea of what the engine was doing at the time the fault occurred. Erase it and it might be that you have deleted valuable clues without fixing anything.
If the engine can now be started and the light has stopped flashing, you should slow down on unnecessary driving and schedule a soon inspection. If it flashes again, or starts shaking or stops working, STOP!
Intermittent faults are still faults! However, they just need more careful testing to reproduce/repair and identify.
Conclusion
When your check engine light flashes, your vehicle is telling you that you should not drive the vehicle as there are likely to be more problems in that direction. Most times, what is important is that a misfire is active causing unburned fuel to head down the exhaust system and put the cat at risk.
Slow down, do not extremely accelerate and stop in safe place. If the engine expends a lot of fuel, starts to heat up, lose power or shake, turn it off and ask to be towed.
Most importantly – don’t replace parts or clear codes without diagnostics. Symptoms may also be caused by a spark plug, coil, injector, a wiring fault or a leaky or mechanical problem. The true cure saves the engine, the time and money and gets the car back on the road safely.
Frequently Asked Questions
What causes the check engine light to flash and car to shake?
Typically, the shaking occurs due to cylinders that are not firing correctly. All the cylinders are no longer putting out equal amount of power, engine will sound bumpy or out of balance. Once you come to a safe stop, notify the driver of the fault causing the shutdown prior to damage to the catalytic converter/other components.
Is It Possibly To Have The Check Engine Light Flash Due To Poor Spark Plugs?
Yes. A damaged, clogged or poorly gapped spark plug may be incapable of sparking the air/fuel mixture. But ignition coils, injectors, wiring faults, vacuum leaks and compression issues can cause the same symptom — a test is better than plug replacement.
Why only flashes when I speed up?
Ignition and fuel system are under greater pressure and strain as a result of acceleration, as is pressure in the cylinders. A weak coil or worn plug, a low fuel pressure or any other fault could cause the engine to run well for a while, and then start to misfire under load.
Will an OBD-II scanner pinpoint for me the item(s) that need to be replaced?
Not usually. The scanner decodes any trouble codes and systems detected. A cylinder-misfire code can be a great starting point, but further testing will be required to determine if an ignition, fuel delivery, air flow, wiring or mechanical compression issue exists.
Will disconnecting the battery clear the flashing check engine light?
This could wipe out the warning, and important information on diagnostics… but won’t cure the problem. The light will again come on if the misfire persists. Read the codes and diagnose the vehicle before clearing anything.
