You should always get a Check/Service Engine Light looked at as soon as is convenient.  However, if a Check/Service Engine Light starts to flash off and on, this usually indicates there is a very serious problem with your vehicle, and you should consider parking the vehicle as soon as it is safe, and call your local AAMCO Center for advice and possibly a tow.

What the Check Engine Light indicates
(see list of OBDII codes)

Since the 1996 model year, cars and trucks sold in the U.S. have featured an on-board computer system to capture problem reports from various systems and to alert the driver to a problem with the vehicle by turning on a Check Engine or Service Engine Light.  Known as the On-Board Diagnostic  system – Generation II or OBDII, this computer system has enough memory to retain code error reports even after the engine is shut off.  This is also true for a short period of time when the problem goes away and then the light goes off on its own.

Earlier  generations do not have this memory and require a scanner reading while the light is on.  Your AAMCO Center will work on the pre-1996 cars, but the method of diagnosing a problem will sometimes slightly change.

Cars and trucks may have 2-4 computer systems in addition to the OBDII computer.  These other computers monitor and control a vehicle’s major systems, such as the engine, transmission, electrical and electronic devices.  These system computers all talk to the OBDII computer and will tell it to turn on the Check Engine Light if a problem is detected.

So, if you have a spark plug that fails, the engine-control computer will detect a misfire in a particular cylinder. After a set number of errors are reported, the engine control computer will send the misfire code to the OBDII system, and it will turn on the check engine light.

In our OBII Transmission Codes post, you will find translation for popular Check Engine Light  code numbers.  This listing may help you gain some understanding of what problem may be igniting the Check Engine Light.

AAMCO Complimentary Check Engine Light Service
When an AAMCO Center offers a free  Check Engine Light service, a technician will plug a scanner into your vehicle.  The technician will tell you what code(s) is triggering the light and advise about next steps. In some cases, a problem has an obvious solution. Other times, additional diagnostic time may be needed as some systems are large or complex.  Also, if multiple codes appear, an experienced technician needs to determine if single repair may be the solution or if there are multiple problems with your vehicle.

My error code starts with a 1 not a 0.  What now?
This will actually happen much of the time.  A four-number error starting with ‘0’ is a generic error code.  If the number starts with a ‘1’, this indicates the manufacturer is using this code to indicate a specific problem(s).  For example, the code P0350 and P1350 both indicate a problem with the ignition coil system. The ‘1’ indicates that the manufacturer (Ford, GM, Toyota, etc.) has additional information about this problem, and this may include subsequent tests that need to be done,. Your AAMCO store has this information in the databases it uses to support the code reading systems it has in Centers.