Do You Really Know What That Check Engine Light Means?

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Reader Question: My check engine light came on the other day what should I do? Will it hurt my car if I continue to drive it?

I hear this line at least once a week. The instrument panel on most cars is absolutely cluttered with warning indicator lights and buzzers. These lights are colour-coordinated so that different colours indicate the severity of the potential problem. As you start the car, all of the lights should come on, and as the computer verifies each component is working properly, the light is turned off. You should only be concerned with lights that remain on for several minutes after the car has been started. Check engine lights can be tricky to repair, so a little help on your part could really save the mechanic some diagnostic time, and save you some money!

     Treat check engine light, and all dash lights like traffic lights.  A Red Warning light indicates an immediate danger. Pull over, turn off the car immediately and assess the problem. Symptoms that usually cause red warning lights are engine over-heating, low oil pressure, transmission over-heating, low battery voltage, and brake failure.

     Red lights can also indicate a safety issue, so proceed with caution as you manoeuvre to stop the vehicle. Unfortunately, when the red light is illuminated the problem is at its peek. It can be a matter of seconds before permanent engine damage occurs.

Some common things to look for when a red light comes on are:

• low anti-freeze, engine oil, and transmission fluid levels

• low brake fluid

• missing belts

• faulty alternator that is not charging the battery or a bad battery

An Amber Warning light, (Usually a Check engine soon light) indicates "Proceed with caution." The onboard computer system has indicated a potential problem and is alerting the driver. This computer system resets and re-tests all sensors and indicators each time the car is started. The computer system is capable of correcting some minor abnormalities, but if the light continues to come on after multiple car starts, it is probably sensing something that would imply a visit to the diagnostic mechanic is in order.

Some common things that may cause an Amber light (Check engine soon light) to come on, but will probably require an experienced technician to diagnose are:

• Anti-lock brake systems

• Safety restraint systems, such as air bags

• Emissions components

• Computer-related problems, such as faulty sensors

If you are driving your car and an amber light comes on, ask yourself these questions:

1. Did you notice problems when starting the car? (slower to start than normal etc.)

2. Have you noticed an increase in fuel consumption recently?

3. What is the over-all running condition of the car? Is the engine misfiring or not performing like normal? Are there any new noises from under the bonnet? Turn off the radio and listen closely as you drive the car.

4. Do you notice any odours, such as a rotten egg smell, or see visible smoke from the exhaust or from under the bonnet?

Make sure to note the exact location and wording of the light that has been coming on, because Murphy's Law dictates that the light will suddenly not come on when you take it in to the garage.

In some cars, "engine" is the more serious red light, whereas others use "check engine light," which is an amber caution light. If the mechanic thinks you are seeing an amber "check engine light," and your car is indicating a red "engine" danger light, this could be a costly mistake for both of you. Why? You could be having a serious over heating problem and the mechanic is assuming you are having a less serious caution light illuminating. The mechanic then might give you the "green light" (no pun intended) to proceed with your day out with the kids. Yikes!

Start the car, and point to the light to ensure good communication of the problem. Intermittent dash warning lights can be a pain and hard to diagnose! Diagnosing the problem in some cases will require the light to be on while the mechanic performs the diagnostic test. If the light is not on when you bring the car to the garage, you might be wasting your time and the mechanic's.

SIDE NOTE: Keep a "running condition and dash light" log in your car to help the mechanic pin point the root of the problem. I have a customer who keeps such an accurate log of her cars' complaints that sometimes I can diagnose the problem correctly with the help of her log and by taking her along on my initial test drive. I can do my diagnosis usually without opening the bonnet to her car. This saves me time and she saves money on a diagnostic charge. This customer can also hold me to my warranty time period, because she had this particular complaint written in her log book.


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