I Just purchased a 1992 Mazda MX-3 GS with the 1.8 V6 engine and the check engine light is on.

I checked the diagnostic codes and it looks like i have codes 15, 16, 17, and 23

15 LHO2S inactivation error
16 Exhaust gas recirculation (EGR) system
17 LHO2S inversion error
23 RHO2S inactivation error

The PO told me that the O2 sensor in bank 2 is throwing the check engine light but i really like to look into things myself before i just go out and buy stuff.

So can anyone help me with what is wrong and if it is only one thing, why is there 4 codes?

Thanks for all of your help!

 

Haarstad:
I don't have the same car as you but I went through a bunch of CEL episodes with a '98 protege.
In your case I would first look into the EGR system. Clean the throttle body and open all EGR ports because they are probably plugged up with gunk. Remove the EGR valvae and clean it out. I scraped mine out because the passages were restricted by deposits.
Then I would check the electrical parts of the HO2 sensors. Look up some Youtubes on how to test oxygen sensors. Test the circuits that go to and from the HO2 sensors as well. You have 2 internal circuits: one for the heater and one for the O2 sensing signal. Externally you have the same circuits and a ground connection.
Also make sure you don't have any vacuum leaks at intake side and make sure that no vacuum lines are clogged. In the protege the nipple that connects the EGR Boost sensor to the intake gets clogged. I pushed a wire in there to open it up.
The Haynes manual is very helpful in providing the values to test for.

Good luck!