1998 Mazda Protege Trouble code help?
 

My friends Protege is up for inspection but she has a CEL so it has to be fixed first.

1998 Mazda Protege
1.5 Liter Automatic

My AutoXray CodeScout 2500 shows the following 3 codes:

P0421
P1195
P0505

Is the any one thing that will set all three or is there more than one problem here?

I know the P0421 is any O2 sensor but which one?

I think the O2 sensor issue is a problem by itself but can the other 2 be related?

Any help much appreciated.

P0505 is idle air control valve easiest way to test this is to unplug the wiring harness going into the iac if your rpm's change you have a vaccum leak if there is no change replace the iac/ P1195 is an egr valve problem it could be a corroded or broken wire in the harness or as easy as cleaning the egr valve/ P0421 unplug your 02 sensors messure the voltage coming off each harness if they are matching you need a new cat converter i had the same code on my gf's car and the cat converter was no good all 3 of these problems are completly diffrent so each one needs to be looked at hope this helps