Rick's Free Auto Repair Advice

Check engine light on – Part I

Why is your check engine light on?

This is Check engine light on – Part 1 of a Two Part series. Want to skip to Part Two to learn how to diagnose? Just click here.

Your check engine light, airbag light, brake light is on and you want to know why. A check engine light turns on because the computer has detected a problem and has set a trouble code in the computer’s memory. There are over 2,000 possible trouble codes related to the engine and transmission alone. There are also at least 2,000 more trouble codes related to brakes, electronics, data circuits, airbags and other safety equipment.

trouble code, check engine light

An example of some of the 3,000 different trouble codes that can turn on your check engine light

So when you post a question like this on a forum, “Why is my check engine light on?” there’s simply no way to answer it. You’re asking us to whip out a crystal ball and guess which of the 2,000 different trouble codes turned on your check engine light.

No one can possible give you an answer with any degree of accuracy.

You have a responsibility to get the trouble codes read BEFORE you ask for help. Any auto parts store can read the trouble codes for free. Or, you can buy a code reader for less than $40.

Getting the code is always the first step in diagnosing a problem. If you won’t do that part, then you have no business asking someone to devote their time and expertise to solving your problem.

So get the trouble code read for free at almost any auto parts store. But DON’T take their advice. The clerks will recommend replacing whatever part is listed in the code. That’s a losing proposition.

Oxygen sensor codes are the most common. So auto parts clerks always recommend changing the sensor. But over 80% of all sensors replaced actually test fine. Remember, trouble code NEVER tell you what to replace, they only tell you the condition they see. So if they’re seeing a lean condition, it could be a bad sensor. But most often it’s a vacuum leak that’s causing the air/fuel mixture to run lean.

To read Part Two of the series, click HERE

To learn more about code readers, click HERE

For more information on trouble code, click HERE on CODES

For more information on trouble code, click HERE on CODES2

For more information on trouble code, click HERE on CODES3

©, 2013 Rick Muscoplat



Posted on by Rick Muscoplat

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