Check Engine Light Flowchart

Follow these steps to narrow down the cause of your check engine light.

Step 1: Read the Code

The first step is always to use an OBD-II scanner to read the Diagnostic Trouble Code(s). Do you have the code?

Yes, I have the code(s)

No, I need a scanner

Step 2: Check for Misfires First

Is the check engine light flashing? Is one of the codes a P03xx code (e.g., P0300, P0301)?

Yes, it's flashing or I have a P03xx code

This is critical. Fix this first.

No, the light is steady

Proceed to the next step.

Step 3: Analyze the Code

What code did you get? If it's P0420, you're in the right place! If not, use our code finder.

It's a P0420 code

Start with our main guide.

It's a different code

Use our code finder tool.