On board diagnostic (OBD)

For vehicles made after 1996, retrieving the codes of the check engine light in your dash panel is simple. All you need to do is find your diagnostic connector located under the dash by the driver side. You can then hook up a scanner and the codes will be displayed for you. If you don’t have any scanner like most drivers, you can bring your vehicle to any local automotive parts store and they will usually scan the codes FREE for you. However, for vehicles made on or before 1995, there is only one cheap way to get it: You do it yourself!

On board diagnostic (OBD) was designed on vehicles equipped with electronic fuel injection so you can generally retrieve the codes yourself. No need buying a scanner or running to any parts stores to check the engine light. This system is called obd1 and applies to most vehicles made before 1995 for domestics and 1993 on imports. In this article, I will discuss the methods used by domestic vehicle manufacturers on how to check the engine lights in their cars and trucks.

For GM domestic vehicles made before 1995, the diagnostic connector is located under the dash panel by the driver side. To get the check engine codes to flash in your dash panel, use a jumper wire or a paper clip and connect terminals A and B of the diagnostic connector. Turn your ignition key on with engine off and the codes should start to blink. All codes should start with code 12 which is one long flash followed by 2 short flashes. This code 12 means the diagnostic system is normal and will repeat itself continuously if there are no trouble codes. Otherwise, code 12 will flash 3 times before flashing the fault codes.

Ford owners can check their check engine light using the diagnostic connector located at the engine compartment by the fender near the battery. Getting the obd1 codes need a couple of tools: a 4 inch long gage 16 jumper wire and a 12 volt test light.
Both tools are hooked up to the diagnostic connector and when the ignition key is turned on (without starting engine) the codes will begin to flash in the test light, not in the dash panel. If there is no code, you will normally get code 11 or 111. On Fords, there are 2 test modes, the KOEO (key on engine off) and the KOER (key on engine running). Both test modes should be used to get the accurate evaluation of the stored fault codes.

Of all the 3 domestic vehicles, the easiest method to check the engine light is Chrysler products. Why? Because all you need is to turn the ignition key on and off a within 5 seconds and the codes will start to flash in the dash panel.

Counting the codes being flashed is almost the same for these 3 domestic vehicles and most of the codes can be erased or cleared by disconnecting the battery negative terminal for 1 minute and reconnect. Just make sure to check your service manual in case you have electronic equipment such as radio or clock that needs reprogramming in which battery disconnection is not recommended. Finally after performing repairs on the culprit code, always go for a road test to confirm if the problem is fixed.

If you want a detailed way on how the above procedures are done, please visit my blog: http://check-engine-light-codes.blogspot.com . This blog offers free info on how to check engine light codes with color pictures and regular repair tips so you can save money next time you see your check engine light.

Author: Richard Trent