This is sometimes called the malfunction indicator lamp (MIL), check engine light (CEL), or service engine soon (SES). But there are others (brake, battery, etc.).
What do I do ??? 😱
(click each step to jump to that section)
Step 0: Check your owner's manual. Sometimes the alert on your I/P is simply to remind you that scheduled service is due.
Step 2: Find out what the result means
NOTE:
If you are posting a question about a trouble code you have, please provide the WHOLE description.
Example: "P0402 - Exhaust Gas Recirculation Flow Excessive Detected"
Step 1: Run a diagnostic scan
The computers in your car are constantly running tests on the various systems to make sure they are working properly. When there's a problem, the computer stores information about it, and alerts the driver.
Every vehicle has diagnostic connector somewhere under the dashboard
This port allows a diagnostic tool to be connected to the vehicle, to retrieve technical information the computer stored about the problem. This information is critical to finding the cause of your trouble light.
- Some auto part dealers such as Autozone, Advance Auto, O’Reilly, etc can scan your vehicle for you, free of charge. (click here to find out more)
- Many auto shops adertise complimentary diagnostic scans (in hopes of getting some business from it). Other shops won't advertise, but they won't charge you for the diagnostic if you ask them to service your vehicle.
- You can purchase your own scan tool. They range from for under $100 to $1,000 and up, depending on the features and capabilities. Click here to see our article about how to choose a diagnostic scan tool.
If the diagnostic scanner finds a fault stored in the vehicle computer, it will identify it with a code called a Diagnostic Trouble Codes (DTC). The code looks like this:
Xyyyy
Where X is a letter and yyyy is a four digit number. For example:
B1410, P0301
etc.
Right away, you can get some basic information simply by looking at the first two characters in the code:
example:
P0302: A standard powertrain problem in the ignition system.
Higher end tools will also tell you exactly what a code means. If yours doesn't, you need to look them up which is easy thanks to the internet. Most of the time, you can simply type your code into a web search, and quickly find the meaning of the code.
(be sure you type letter-number-number-number-number. It's pee-zero-301, not pee-oh-301)
Your vehicle's computer also records what the engine is doing and sensor values at the time of the failure. (Engine temperature, throttle position, speed etc.) This is referred to as freeze frame data, and a good diagnostic tool can also recover this. This can help you replicate and troubleshoot the problem.
- OBD-CODES.com is an excellent website for looking up codes.
It will provide you the meanings, possible causes and solutions to most trouble codes.
- Repairpal.com - Most Common OBD-II Trouble Codes
Step 3: Fix the problem
Don't be a parts changer
When you see "P0138 - O2 Oxygen Sensor Circuit High", don't just run out and buy a new oxygen sensor. Take the time to find out what the trouble code actually means, and find the source of the problem. For example, sensors can cost hundreds of dollars, so you could spend a lot of money on a new one, and just end up with the same trouble light, because the problem was actually caused by a $1 fuse, or a broken wire somewhere else.
Websites like obd-codes.com provide detailed step-by-step instructions on how to verify where the problem actually lies. Trouble codes don't tell you which parts to change. They are clues to finding out what's wrong.
Scotty Videos
- Trouble light and what it means
https://www.youtube.com/watch?v=CgC7E0YBknU - Don't guess
https://www.youtube.com/watch?v=svDzJMEnVD0