I have a 2005 Mazda Tribute 3.0. About a month ago I had the engine light come on, I immediately checked the codes. p0443 ( Purge valve solenoid ) p0403 ( egr solenoid ) and all 4 o2 sensors p0 135 141 155 161. ( o2 heater circuit ) All 6 codes are electrical circuit related. I have checked the o2 fuse and it is fine ( replaced it anyway ) These parts did not all fail at the same time. I removed purge solenoid and energised , it clicked and allowed air to pass through it, seems to have no issues. I replaced the egr vacuum solenoid, since it is a common failed part. The egr valve itself holds vacuum no problem. I tested for 12 volts leading to purge solenoid and egr vacuum solenoid. They both have 12 volts. I tested between the egr solenoid and pcm for 12 volts, it has 12 volts as it should, it is pcm ground side switched. I have not tested the o2 sensors for power, but I have inspected the wires
and they seem ok.

I have checked the PCM harness and the wires seem ok. I have checked for vacuum leaks and cannot find any. The car ran fine for weeks after the codes were set. It now runs fine until the codes are set and then runs rough at idle.
I do not drive the car and I will not until I can sort the issue. It could be PCM related? I applied a vacuum gauge to egr and road tested it. The egr solenoid is opening and passing vacuum to egr valve as it should. Apply throttle and the solenoid opens egr, let go of gas and immediately no vacuum to egr, seems normal to me, yet still the p0403 egr electrical code. I do not believe any of the parts are bad, also i cant see bad o2 sensors causing a purge valve and egr solenoid electrical codes. I could understand a bad egr system causing o2 codes, but not necessarily, o2 heater circuit codes. I was thinking pcm issues, but seeing the egr solenoid seemingly working as it should, passing vacuum to valve, that seems to imply pcm is doing as it should, completing the circuit. I have power to dpfe sensor as well, not sure how a bad dpfe could cause purge code circuit and o2 codes circuit.

I had 58 miles with no codes and all my monitors were ready. CEL came on during inspection and all 6 codes were back. they now come back as soon as engine is warm.

At a loss here.