Why Is My Check Engine Light Flashing? 

why is my check engine light flashing?

Every car owner knows the worry that comes with having to ask, “Why is my check engine light flashing?” Part of the reason a flashing engine light is so nerve-wracking (and why people might be tempted to ignore it) is that a flashing light doesn’t tell you what’s going on with your car — only that something is wrong.

While it’s impossible to tell exactly what’s wrong with your engine without running a code test first, you can still clear up quite a few mysteries — including whether you need to take your car in immediately — with a general knowledge of why your engine light turns on.

If you find this blog helpful, check out our other posts on your car’s dashboard lights:

An overview of your check engine light: The ECM, OBD, DTCs, and CELs

Here is a rough order-of-operations that might lead to your car’s check engine light flashing:

  1. Your car’s computer, known as the electronic control module (ECM), is constantly scanning your car for potential issues. When the ECM discovers a problem, it tries to fix it on the first try.
  2. If it can’t fix the problem and if the problem doesn’t correct itself, the ECM will wait for a few cycles and try fixing it again.
  3.  If the problem is still not resolved, the ECM reports it to your car’s on-board diagnostic system.
  4. Your car’s OBD-II checks the problem and stores what it finds as a diagnostic trouble code (DTC).
  5. After the DTC has been stored by the OBD-II, the appropriate light on your car’s dash will be triggered. If your engine is causing the problem, the check engine light (CEL) or service engine soon (SES) light will turn on.
  6.  Depending on the issue your engine is experiencing, the CEL will either flash then go off, flash constantly, or remain on continuously.

Why is my check engine light flashing constantly?

If your check engine light is flashing constantly, it’s telling you that your engine is having the kind of problems that could quickly turn serious. These problems include eventual damage to your exhaust system and your catalytic converter, both of which are very expensive to replace. 

Long story short: If your check engine light is flashing constantly, get your car to a service specialist as soon as possible. Your car and your wallet will thank you later.

What if my check engine light is flashing intermittently?

We often receive calls from customers asking, “What does it mean when your check engine light flashes, then goes off?” 

Intermittent flashing of your check engine light occurs when your engine experiences what’s called either an “intermittent failure” or “soft failure.” Soft failures are caused by engine problems that need certain conditions to appear.

The most common example of an intermittent failure is that of broken wires. Broken wires can connect and disconnect when there are bumps in the road, thus causing your engine light to turn off and on.

Why is my check engine light continuously illuminated?

While not exactly good news, a check engine light that’s continuously illuminated indicates less serious (but still important) engine problems. Make an appointment with your local repair shop and take your car in as soon as possible.

What should I do when my engine light is flashing?

If you can’t answer the question “Why is my engine light flashing?”  on your own, then it’s time to make a visit to Colony One Auto Repair. While we typically support those with a DIY spirit, only experienced mechanics should tackle serious engine issues.

Even if you have an at-home OBD-II reader, the DTC can only tell you so much without you getting under the hood. The sooner we are able to take a look at your car, the better your chances of avoiding additional, expensive repairs.

The professional service specialists at Colony One Auto Repair are here to help with any and all engine problems, from check engine lights to blue smoke coming out of your exhaust pipe to understanding the ins and outs of your engine, oil, and overheating problems.


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