Hey fellas,
So I got a 92 hatch with an internally stock 99 b16a2 with just bolt-ons: DC ceramic header, Magnaflow hi-cat, and the rest of the exhaust ITR, for the intake AEM with a bypass. I've had this code for some time now and cannot for the life of me solve this and I am about to throw in the towel to my mechanic. When I bought the car it already had the swap done, I got the code many months after I purchased it and replaced the O2 sensor. Surely enough it did not solve the problem and looked at some of the diagnostics behind it stating to check the harness, look for exhaust leaks, and a bad o2 sensor. Well, I ruled out the o2 sensor looked at the harness and look fine, no wires were frayed, melted, etc. Next, I resulted to the DC header put a rag by the exhaust tip to hear any leaks and nothing by the header exhaust ports nor under the vehicle near the O2.
Being stumped I took it to my mechanic and hooked it up to his scanner and watched the oscilloscope do its job, we saw perfect health out of the O2 sensor and was functioning fine. However, we did notice the PCM or ECU whatever you like to denote it as was bad. So I replaced it with a low mileage P2T still, didn't resolve the problem. When I get the code checked it pops up as P0133, next I got out my multimeter and checked voltage from the harness. I had the ground probe on the negative end of the battery and had power on the voltage end of the harness don't recall the color of wire. Didn't show any voltage with the ignition on. Now I do have a new OEM exhaust manifold gasket that came with the car when I got it so I might try that next just to narrow it down. Anyhow, I was wondering if you guys can give me further insight into what's possibly going wrong or any additional things I should do would be greatly appreciated.

Thanks