96 O2 Problems, running out of ideas!

Long story short
truck is a ODBII f150, 302 engine
manifolds were cracked, put on long tubes
welded in nuts for the O2s to screw in at the collectors
wiring didnt work, made some homebrew O2 extensions
bolted up headers, clamped some mufflers right onto the headers
installed brand new upstreams o2's
downstream o2 stuff in muffler exhaust for now (shutup, i know)

Problem is engine runs really rouch, smells like its running rich.

At initial start engine runs good. Approx a 10-15 seconds after starting the engine short term fuel trims steadly shoot up to 32% (max). Engine stays in open loop. All 3 O2 Voltages stay pretty steady at 0.275-0.310 Volts. Reving the engine at high RPMS will eventually send the O2 voltages up, and trims will come down. but after it cools down, back to 32% rich. Long terms are pegged at 25% Btw.

The code that pulls is P0115 (HO2B2S1 heater circuit). After clearing the code, it will come back just seconds after starting the car.

Swapped upstream O2 from bank 1 to bank 2 - no change.

Checked HO2B2S1 heater power pin for voltage at sensor connector - Good

Disconnected PCM, Checked contunity between HO2B2S1 sensor connector and at PCM harness 0hms - Good

Checked heater resistance of HO2B2S1 at connector, and at PCM harness 4ohms - good

Checked for shorts between HO2B2S1 case and all pins - no shorts - good

Checked for shorts between HO2B2S1 GND amd PCM harness pins 24, 76, 103, 91 and 97 - no shorts - good


The Last step of the troubleshooting guide in the service manual confuses me, and im not sure what its asking. It says this following:

"Use the following list to measure the resistance between the appropriate test pins at the breakout box and the ho2s htr gnd at the harness connector.
Ho2S HTR-11 Test Pin 93 (Htr Gnd)
Ho2S HTR-12 Test Pin 94 (Htr Gnd)
Ho2S HTR-21 Test Pin 95 (Htr Gnd)
Ho2S HTR-22 Test Pin 96 (Htr Gnd)
Is resistance less the 4.0 ohms?
Yes: Open or shorted or excessive resistance in the heater circuit in the PCM replace PCM
No: Repair open or excessive resistnace in the heater circuit in harness."

I also T-Pinned all 3 Ho2S HTR Gnds at the PCM connector when the engine is on. I get a reading of 14 Volts on all 3, and a resistnace to ground that cyles on and off, i would say 80 percent of the time 0hms, 20 percent Open. Looks like normal operation.

Cleared codes multiple times, P0115 keeps coming back. Short of chaning the PCM in out of ideas. I dont think the downstream is preventing it from going closed loop.

Anyone ?

 

You didn't put the same O2 sensors in all 3 locations did you? The ones for the front are a different part number and function differently than the downstream sensor.

 

they "should" be the right ones, i will have to double check the part numbers.

 

this is the last troubleshooting step i dont understand
does it make any sense to you?
https://i.imgur.com/U2KKc5F.png

 

They just want you to test continuity of all 4 wires in the O2 harness from the O2 connectors back to the PCM connector.