Check Engine Light Repair - What to Do If the Warning Comes on the Dash of Your Car Or Truck

Today's GM vehicles use many sensors, switches, solenoids, and other electrical components to control or monitor every aspect of the engine. From controlling the fuel and ignition systems, to monitoring the emissions. A problem in any of these systems, or subsystems, can cause the check engine light to come on. If the engine light is flashing, this is a sign of an engine misfire that is bad enough to cause damage the the catalytic converter. This should be looked into as soon as possible, since replacement of this component can be very expensive. Even if the warning goes out by itself at some point, there will still be a trouble code stored. This does not mean the problem has resolved itself, it just means the fault is not occurring at this particular time. This can indicate an intermittent problem. Intermittent problems can be the most difficult to diagnose and repair.

The first step in any diagnosis of the check engine light is to get the computer (PCM or ECM) scanned for codes. Any time this warning comes on, a code is stored in the computer memory along with many data parameters that were present at the time of the fault.

A simple code reader that can be purchased at any automotive supplier can retrieve these codes. Many of the large national parts store chains will scan the system at no charge. The code will give an indication as to what system has / had a problem. The more expensive scanners will also show live data, and allow further diagnosis by being able to control parts of a particular system.

In order to scan your car for codes, you must first locate the diagnostic connector. It will be under the drivers side dash. If you do not have a car code reader, many of the large national parts store chains will scan your cars computer for free.

On today's newer vehicles (1996-and up, OBDII), the diagnostic terminal is what powers up the scan tool. If the scan tool does not power up after plugging in to the connector, you will need to check fuses. Different vehicles use different fuses to power this connector.

After reading the codes(s) and the short description, you will need to use a diagnostic chart to pinpoint the problem. Just because the scanner shows, lets say, a code for the intake air temp.sensor, does not necessarily mean that the sensor is bad.