My Check Engine Light Is Flashing: What Should I Do?

By Karen Johnston June 22, 2011

Quick facts

A steady check engine light = a stored code; schedule service soon
A flashing check engine light = active misfire damaging the catalytic converter; stop driving
The computer stores a fault code even after the light turns off. It can still be read.
Clearing codes without fixing the problem will cause the light to return

When the Check Engine or Service Engine Soon light illuminates on your dash, it means that your vehicle's computer recognizes that there is a system or sensor that is working out of its proper parameters. This indicates a problem. The computer tries to compensate for that problem and keep the vehicle running as close to normal as possible.

Flashing check engine light

When the Check Engine or Service Engine Soon light starts flashing, this means that a catalytic converter damaging condition is occurring. Usually you will be able to feel a noticeable difference in the performance of your vehicle. When this Check Engine or Service Engine Soon light flashes you should pull over safely and shut the vehicle off. Have the vehicle towed to your trusted repair facility for a diagnosis and repair. Continuing to drive this vehicle in this condition will do further damage and could cost more to repair. Depending on the type and age of the vehicle you drive, there is a huge variance on the replacement cost of a catalytic converter.

California emissions standards

The other thing to look at is that many vehicles driven in the Pacific Northwest are manufactured to meet California Emissions Standards. What that means to you is that if the catalytic converter in your vehicle fails, it needs to be replaced with a catalytic converter that meets California Emissions Standards, otherwise it will not coincide with the emissions calibration on your vehicle's computer and could still signal a catalytic converter efficiency code, which will illuminate your Check Engine or Service Engine Soon light. When your light is illuminated or if there are current codes stored in the computer of your vehicle, it will not pass DEQ.

There are pros and cons to your vehicle meeting California Emissions Standards. The pro is that your vehicle runs much cleaner for our environment since California holds higher standards than Oregon. The con is that they have emission devices installed on them that Federal Emission Vehicles do not and the catalytic converter that is original equipment is impregnated with a lot more precious metals, making the cost of the correct replacement part substantially more.

Should I buy a vehicle with its check engine light on?

One other thing to keep in mind is that if you are shopping for a new car, it is not advisable to purchase one with a Check Engine or Service Engine Soon light on. If you are really interested in the vehicle, invest in having it professionally diagnosed before the purchase. Then you can make an informed decision as to whether the vehicle is worth buying based on the repair that is needed. Remember, whenever your Check Engine or Service Engine light is on, your vehicle is most likely not meeting Oregon's emission standards and it will not pass DEQ. When it is flashing, the condition the computer sees is a catalytic converter damaging condition. We would not recommend continuing to drive the vehicle. Either way, it is advisable to have it brought to your trusted repair facility for a diagnosis and repair.

Frequently asked questions

Common questions

What is the difference between a steady and a flashing check engine light?

A steady check engine light means the vehicle's computer has stored a fault code for a system operating outside its normal parameters. It warrants a diagnosis but is not an emergency. Schedule an appointment within a few days. A flashing check engine light is urgent. It indicates an active engine misfire severe enough to damage the catalytic converter with each passing second. Pull over safely, shut off the engine, and have the vehicle towed. Do not continue driving.

Will the check engine light go away on its own?

Sometimes. If the condition that triggered the code resolves itself, such as a loose gas cap that was tightened, a brief sensor fault that did not recur, the light may turn off after a set number of drive cycles without the fault repeating. However, the code remains stored in the vehicle's computer even after the light turns off. A technician can retrieve it and determine whether the problem was truly resolved or is likely to return. A light that turns off on its own should still be checked.

Can I check the code myself with an OBD2 scanner?

Yes. An OBD2 scanner (available at auto parts stores for under $30 or as a Bluetooth adapter) can retrieve the stored fault code. The code tells you which system triggered the light. For example, P0420 indicates a catalytic converter efficiency problem. What it cannot tell you is why that system triggered: whether it is the sensor, the component, or a downstream problem causing a false reading. Reading a code is a starting point for diagnosis, not a diagnosis in itself. Replacing parts based on the code alone without testing the circuit often leads to unnecessary expense.

Schedule service

All About Automotive — 1850 NW Burnside Rd, Gresham, OR · (503) 465-2926

Book an appointment Browse services More articles