ALT-2 What to do when the Check Engine Light is on
To understand the CHECK ENGINE light it is necessary to understand why it is present.
As cars transitioned from carbureted machines to fuel injection and with the push for fuel economy, the car became computerized. An Electronic Control Unit or ECU monitors and controls many aspects of a vehicle as it moves along the country's highways and byways.
This change to computerization also allowed for the creation and use of on board diagnostic software. This software was initially utilized to help clean the air. It would light a lamp on the dashboard indicating the computer had received a parameter that is out of specification for that system or component.
The SERVICE ENGINE or CHECK ENGINE light is a dashboard warning light that hopefully only illuminates during that brief period when you are initially starting your car.
If it comes on while driving, do not panic. It is not possible to tell from just this light if the problem is of a serious nature or a minor issue. Listen to the engine. If it sounds normal, your best bet it to get your car to a shop in the near future. If the car engine is not sounding normal, consider immediately parking the car or heading directly to a shop within a reasonably short distance.
What could be a minor issue? Many new vehicles today require that the gas cap be tightly fastened after refueling. If this is not done, within a few starts the CHECK ENGINE light will come on causing a sinking feeling in the pit of your stomach and wallet.
Tightening the gas cap may not clear the light, even if it was the cause of it to begin with. Some vehicles may require 20-50 starting cycles before the computer clears the code while other cars may never clear it, even if the problem has been corrected.
Does a misfire code in conjunction with an O2 Sensor code mean you must replace the O2 Sensor?
Typically a misfire can be caused by a problem ranging from a malfunctioning spark plug, injector, plug wire, or coil (however, this is only the short list.) This malfunction can then lead to raw gas being dumped into the exhaust because the cylinder is not firing or not firing correctly leaving unburned gas to flow into the exhaust system where it can foul the O2 sensor and click on a second code. In this case, correcting the misfire will correct the O2 code, so O2 sensor replacement most likely will not be necessary. An exception to this is if it is allowed to occur for an extended period of time, the sensor could ultimately be damaged.
Depending on your vehicle, there are many things that can cause a code to light the light.
Understanding that getting the code read in a timely manner will be half your battle and begin the process of correctly clearing this light.
There are many avenues in getting your code identified to begin the troubleshooting phase.
Mechanics typically may charge a fee. You can also purchase a code reader OBD II is the Onboard Diagnostic 2nd Generation system most cars went to beginning in 1996 (with a few exceptions). This benefited many because now one scanner could read multiple cars instead of having to buy a specific scanner for each manufacturer's vehicle.
Local auto parts stores, such as Auto Zone, will read this code for free on your vehicle, if it is OBD II equipped. They will then identify the most common causes for that particular code or codes to be displayed and provide you with a printout.
If you are given a list, remember it is best to start with the cheapest, easiest to perform first as those are typically the most common causes of the code. Also be wary of a repair shop that starts with the higher dollar repairs on this list first.
You can purchase a "CAR CHIP" from a store or online. This chip resides in your OBD II port at all times and can monitor your car's parameters such as water temperature, timing, car speed, hard braking cycles, etc (provided sensors are present in your car to allow for this). This is also a nifty tool for monitoring young teenage drivers' driving habits. This device can be used to identify codes and to clear them after repairs have been made.
Whichever method you determine is best for you, always remember that clearing the codes should only be done after the problem has been identified and corrected. If you have done this, clearing the code should result in the code not repeating again in the near future.
If your light again comes on, either the problem has not been corrected or it is something else. NEVER clear the code just to have the light off. In rare cases, the code could be indicating a far worse problem, but with only the light on the dash, it is impossible to make this determination.
Older vehicles may require a manufacturer specific code reader if going to a mechanic is not financially an option. Many scanners of this type are priced as low as $30 and up.
Some vehicles, such as older Nissans (1986 or so) equipped with computer modules, contain built in diagnostics that can be activated by simply switching a selector on the module itself (usually under the driver's seat) and the red and green lights will flash the codes. Decoding the codes requires a manual, such as the manufacturer's manual or possibly a Haynes or Chilton's manual.
Whatever the year or make of your vehicle, a CHECK ENGINE or SERVICE ENGINE light should not be ignored, even if you believe you know the cause for its illumination. Options for 1996 and newer are widely offered, many free of charge, to help you get your car operating correctly. The light coming on may not necessarily indicate a full-blown major problem, but in some cases, ignoring the light can ultimately lead to additional damage, poor fuel economy, and other more costly repairs that could have been resolved for lower costs if caught earlier.
