DISCUSSION:

The RX-7 was one of the first cars on the planet that had error checking capabilities built right into the ECU (Emission control unit).  Most cars of the time required you to take the car to a dealer and hook the engine computer up to a special monitoring device that will tell you if all the sensors of the car are working properly.  RX-7's being an advanced automobile have this error checking ability built right into the car.  This gives owners the ability to check engine sensors without having to take their cars to the dealer.   

Now before we get to checking the codes, I once again have to distinguish the differences between 86-88 models and 89-91 models...  The 86-88 cars require you to build a test lamp assembly to pull the codes from the computer similar to the one used to adjust the TPS.   The 89-91 cars do not require a test lamp.  89-91 cars use the check engine light inside the car for output signals.  I will describe both processes here in this article...

On a side note, the information contained in this article is referenced from Haynes Computer Codes Manual #10205 and the Mazda RX-7 1986 EGI Rotary Engine Troubleshooting Manual.