With the design of the Honda engine control unit (ECU), an error system was implemented when a vital engine sensor stopped reading correctly.  The error system that was implemented used "codes", or a series of blinking "CELs" or check engine light to signify the faulty sensor(s).  The check engine light is located on the gauge cluster, and when lit solidly, signifies a sensor issue.  It can be as simple as a single sensor, or as complex as multiple sensors causing the CEL to be activated.  For 92-01 Acura Integras, 92-00 Honda Civics, 92-00 Honda Accords, 92-01 Honda Preludes and 93-98 Honda Del Sol you can find out specifically what the CEL pertains too. 

On the vehicles and years listed previously, there is a "service connector" located under the dash on the passenger side kick panel area right above the ECU.  You will find a green rubber termination panel that holds the service connector plug.  It is the plug that has two wires.  In order to check the code, you will need to jump the service connector plug.  The simplest method is to use a paper clip, and bend it into a "U" shape.  Take each end of the paper clip and place them as deep as possible into the service connector plug ends.  Once you have done this, turn the ignition key to the second "on" position, with the engine off.  This will allow the check engine light to illuminate and display the codes.  With the service connector plug enabled, you will see the CEL start flashing (if you have a code, if not you either are not making good contact with the paper clip or you have a bad ECU). 

The "code" system that Honda implemented is one of flashing the CEL for a series of blinks, and varying the duration of the blinks much like morse code.  The long duration blink signifies the first numeric value, and the short duration blink signifies the second numeric value.  For example if you have four long blinks, with one short blink this would signify a code 41.  If you had two long blinks, it would signify a code 20.  If you had 4 short blinks, it would signify a code 4.  If you have several codes at the same time, there will be a short break between each code displayed.  Now that you know how to check the CEL, lets move onto what the codes represent.

You will notice that the list contains the codes, pertaining sensor, problem and solution.  This was done to give a better idea as to what you can do to solve the issue before a tuning appointment.  With the solution portion of the chart you will find that many list to check wiring, or to make sure a sensor is plugged in and correct.  While sensors do go bad, 99% of the time a check engine light on a modified car is due to a wiring issue.  Some of the more common issues that we see are wires that are loose in the ECU pin locations, cut wiring, incorrect grounds and improper sensor plug location.  You will notice that the solution chart has many of the sensors listed that are not vital, and can be disabled when coming for a tuning appointment.  Please make sure that you check  that your particular code is not vital, and do not assume its not.  Codes such as 4, 8 and 9 can be very time consuming to track down and troubleshoot in most cases. 

If you find the issue that is creating your code(s), and want to "reset" the ECU so that the CEL does not illuminate you will need to remove the 15 amp fuse located in the engine compartment.  With the ignition key off, wait approximately 30 seconds, than place the fuse back into the holder.   This will erase the previous codes retained in the ecu, and if the issue is fixed the CEL will be off.  This article was written to give an easy access to finding your CEL codes on a OBD-1 Honda.  If you need more in depth explanation of the code, or a wiring schematic Evans Tuning strongly suggests purchasing a "shop manual" for your particular vehicle.