The "Check Engine" Light: What to Do When It Comes on
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The "Check Engine" Light: What to Do When It Comes on

Of all the “Idiot Lights” on your car or truck's instrument panel, the “Check Engine” light is one of the lights that provides the least useful information. If you are like most motorist today, you will have little understanding of what the “Check Engine” light is really trying to tell you about your vehicle and panic sets in. The worse thoughts possible begins to race through your mind, one after another. “Is my engine about to blow up on me?” “Will I cause some irreparable damage to the expensive on-board electronics if I keep driving my car?” “Do I need to pull over and stop immediately and call AAA for a tow?” In most cases the answers to all those panic questions is a “NO”. The “Check Engine” light could indicate a serious problem that portends an expensive repair or something that will takes you a couple of minutes to rectify yourself.

Of all the “Idiot Lights” on your car or truck's instrument panel, the “Check Engine” light is one of the lights that provides the least useful information. If you are like most motorist today, you will have little understanding of what the “Check Engine” light is really trying to tell you about your vehicle and panic sets in. The worse thoughts possible begins to race through your mind, one after another. “Is my engine about to blow up on me?” “Will I cause some irreparable damage to the expensive on-board electronics if I keep driving my car?” “Do I need to pull over and stop immediately and call AAA for a tow?” In most cases the answers to all those panic questions is a “NO”. The “Check Engine” light could indicate a serious problem that portends an expensive repair or something that will takes you a couple of minutes to rectify yourself.

On-Board Diagnostic Systems

Today's hi-tech vehicles have on-board computers that are capable of diagnosing the problem when something goes amiss with one of their systems, much in the same way as your home computer has programs that allow them to diagnose what is ailing them. However, unlike your computer that provides you with error messages that clues you in to what is really going on, all your car does is illuminate an idiot light, the “Check Engine” idiot light. The on-board computer has the same capability to provide you with an accurate error code too, just as your home computer provides you, but you need the proper OBD Reader to plug into the on-board computer to access those codes.

The On-Board Computer

Beginning in the 1980s, automobiles have become increasingly computer controlled. In today's cars and trucks, computer monitor and control everything –your engines RPM, throttle settings, timing, fuel injection, cooling fans, oil pressure, engine emissions, and automatic transmission shift points, to name just a few. The on-board computer systems and their software components have advanced to the point where they not only control these systems but they recognize when they go amiss and even attempt to correct the problems themselves. When the on-board computer cannot correct the problem themselves, they notify the driver by turning on the “Check Engine” or “Service Engine” light. Basically, the “Check Engine” light can be triggered by anything that effects engine emissions.

What to do when the “Check Engine” Light comes on.

There are two things that you do not want to do. The first thing that you do not want to do is to ignore the “Check Engine” light and just keep driving your car day in and day out. That could lead to some very expensive repairs at some point down the road. The second thing that you do not ant to do is to rush your car to the nearest garage—that can cost big bucks too—because the problem might something that you can remedy yourself in few minutes.

The first thing that you want to do is to scan the instrument panel to see if there are any other “Idiot Lights” lit up to indicate what the problem might be. Check the dash mounted gauges too, if you have any.

An overheating engine can trigger the “Check Engine” light. Is the coolant system idiot light on or is the temperature gauge reading in the Red? The problem may be as simple as being low on coolant and adding coolant will solve the problem. Of course a problem with the cooling system could be something more serious too, like a failing water pump, a malfunctioning thermostat, or leaking radiator hose. Check the coolant level before taking you car to the garage.

Check to see if the oil pressure light is on. Low oil pressure can trigger the “Check Engine” light. Low oil pressure may simply mean that you need to add oil to your engines crankcase, so pull the dip stick and check the oil level before taking your car to the garage. Off course if there is enough oil in your engine the oil pressure “idiot Light” may mean that you have a failing oil pump, clogged oil filter, or some other problem that will require professional attention.

If none of the other “Idiot Lights” are on and/or all the gauge read normal, check your gas cap. I know that may sound silly to you, but a loose gas cap will cause the “Check Engine” light to come on and stay on. As I said earlier in this article, the “Check Engine” light will react to anything compromising Emission Controls. A loose gas cap compromises the sealed gasoline vapor recirculation system by allowing gasoline vapor to escape into the atmosphere. The on-board computer will detect this and fire up the “Check Engine” light.

If your car is equipped with OnStar, call them. The factory installed OnStar system can communicate with all you cars on-board computers, so the OnStar operator can read the troubles code remotely and advise you what steps you need to take. They can advise you if its something you can fix, if it is safe to continue driving your car, or if you need to pull over and wait for the operator to send a tow truck.

If your car is not equipped with OnStar, take it in to an auto parts store like Auto Zone or Advanced Auto Parts. Stores such as these have the equipment to read your cars trouble codes and they performed those checks free of charge. They do not charge for the service because they hope that you will buy what ever parts you need to fix your car from them.

After exhausting all these option, it is time to take your car to the dealer to be checked and serviced.

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Comments (15)

I hate car problems. I was going over Red Mountain Pass a few years ago when the "Check Engine" light came on. I was scared--are my brakes about to give out? do I need transmission fluid? Not here, not now! Anyway, it turned out to be a loose wire. Geeeeezzz!

I had it happen to me and as you said it was just the gas cap

WOW! A detailed instructional and elaborate read.

I think the most common reason for the check engine light to come is, as Brenda mentioned, a loose gas cap. The second is 'low tire pressure'. So if it does happen there should be no need to panic, although I usually do.

Yep... I had a loose gas cap that triggered the check engine light. The loose gas cap also caused the car to run hot.

Thank you for this valuable information.

Like Sandy, I hate car problems. I get panicky so easily.

Jerry, you are always the best. I am trying to fix my Skype to talk with you. I do not know if it is my computer or the program, but as soon as I have it up an running, I promise to stay in touch. Either way, your articles remain the best.

I am sorry I am out of votes so I Tweeted this.

Well, Jerry..that idiot check engine light cost $89.00 just to check it not to mention what it cost to fix it...voted

Ranked #1 in Car Repairs

@Francina Marie. Yes, just having the diagnoses at a dealership or regular auto service center is expensive, that's why I mentioned that you can have the codes read for free at Auto Zone and Advanced Auto Parts stores.

Ranked #7 in Car Repairs

Great information.

The article title caught my attention right away. How did you know? LOL Very useful and timely post. Thanks for posting valuable information here, I'm most appreciative. Voted!

I had that happen to me with the loose gas cap triggering the engine light on my dashboard. These are great, practical steps for car owners to follow. Thanks Jerry.

It used to come on for my Camaro all the time. It was a false sensor. Check engine light – check wallet too.

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