What Does the Check Engine Light Really Mean?

Billshark knows that sick feeling in the pit of the stomach that happens when your check engine light pops on. Should you stop driving? Get a tow? Start planning for a major repair bill? Not necessarily.

What is a check engine light?

Since the 1980s, automakers have been incorporating more and more computer functions into their cars. One of these is an onboard diagnostic system that can provide drivers with useful information.

Depending on the make, model, and model year, the check engine light—found on the dashboard—can be a picture of an engine, possibly with the word “check” above or below it, and be either amber, yellow, or orange. In older models, the words “check engine”—which can be any color—appear. Other similar warnings might say “check powertrain” or “service engine soon.”

But is it serious?

When the check engine light comes on, it can be anything from a change in humidity to a significant engine malfunction. In most cases, there’s no need to panic, or even to stop driving immediately. Unless you feel the car begin to behave strangely, particularly if it starts losing power, you can usually finish your trip. If it’s simply a change in atmospheric humidity, the light will go off quickly.

Serious signs that require immediate attention will typically include other warning indicators on the dashboard: engine overheating, low oil pressure, or a red or flashing check engine light. In this case, pull off the road as soon as you can and call a tow truck.

Unfortunately, although you can buy a diagnostic tool that deciphers the diagnostic code, even those familiar with automobile engines may have trouble pinpointing the cause of the light.

A loose gas cap is one of the most frequent triggers of a check-engine warning. The onboard diagnostic system is designed, among other purposes, to monitor for environmental pollutants emitted by the engine, and a loose or damaged gas cap will cause the light to illuminate.

Modern gas caps must be tightened until you hear and feel at least one “click.” To see whether a loose gas cap is the problem, unscrew it and screw it back in until it clicks. It may take several trips for the computer’s light to reset, but if the light doesn’t go out in a day or so of driving, you need to have a qualified service technician diagnose and repair the problem.

Don’t fear the repair bill

Some people, fearing a costly repair bill, will ignore the check engine light. This is a classic example of being penny wise and pound foolish. If you ignore the light, you risk damaging components that can be even more costly to repair, rather than nipping the problem in the bud.

Edmunds recently provided a list published by automotive telematics company CarMD showing the 10 most common triggers of a check engine light, and the estimated cost to repair each of them.

They are:

  1. Replace ignition coil(s) and spark plug(s) ($391.42)
  2. Replace oxygen sensor(s) ($244.04)
  3. Replace catalytic converter with a new OEM catalytic converter ($1,371)
  4. Check for loose gas cap, tighten or replace ($25.86)
  5. Replace ignition coil(s) ($217.91)
  6. Replace evaporative emissions purge control valve ($149.52)
  7. Replace mass airflow sensor ($340.58)
  8. Replace evaporative emissions purge solenoid ($153.70)
  9. Replace fuel injector(s) ($449.73)
  10. Replace thermostat ($244.61)

As you can see, with a couple of exceptions, these repair bills are not huge, but if left unattended, could end up damaging far more expensive engine components, costing you far more eventually.

If you need extra cash to cover things like this, why not let Billshark review your bills? You only pay if we can save you money.

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