86 Squarebody with 5.3L LS and P0174 Lean Bank 2 code

[shortboxin]

Swapped in a 2004 Chevy 4.8L VIN V using a Chinese Amazon standalone wiring harness (BAD IDEA). Initially, I found 8 miswires on the Chinese harness by checking continuity for each point on the PCM to it’s expected destination and then for shorts from each point on the PCM to all other pins of the PCM. That engine died after one drive. The replacement engine is a 2004 Chevy 5.3L with a VIN Z (flex fuel). I am using the 4.8L injectors, throttle body, MAF, and computer. To complicate things more, I drove the truck once and then decided to change the factory truck intake to a 92mm sheet metal Amazon model. I never looked at codes or real time data on my code scanner prior to swapping so I don’t have a good baseline on anything (ANOTHER BAD IDEA).

Truck smells rich, gets P0174 lean bank 2 code, bank 2 ST fuel trim at idle is around 25% and O2S21 is at 0.00V. My bank 1 fuel trim moves around, but is typically very low under 5% at idel and the O2S11 reads around 700mV.

Initially, I treated this problem as a vacuum leak or injector issue. Using an infrared thermo, not quite full temp I was getting around 180 deg F at each header port on both banks, so it looks like all injectors are working. I'm running Chinese shorty headers, not cast manifolds (don't know if this matters). Shot it with some starter fluid around all intake ports and injectors, no noticeable change in idle.

Double checked all of my passenger header and collector bolts and torqued up a little more just in case. Still the same data on the scanner.

Unplugged my computer again and verified continuity from my O2 Signal Hi and Low for both banks to the PCM (all good) and checked each pin to all other pins on the PCM for shorts as well (nothing found).

Tried to read a voltage on the Signal Hi to GND for both banks at idle using my DMM. Bank 1 was flashing all over the place from 200mV to 1.2V while bank 2 was a fairly steady 50mV to 60mV. Don't know if that was a floating value or what because the PCM displays 0V for O2S21 which I assume is the value read from the O2 Signal Hi to GND.

Started up the truck and read real time data with the O2s connected normally. I then installed an O2 extension harnesses where I swapped the O2s so that bank 1 O2 fed bank 2 PCM connection and bank 2 O2 fed bank 1 PCM connection. Got the same results both ways:

STD CONNECTION(bank 1 to 1 and bank 2 to 2)

O2S11 800mV range
O2S21 0.00V


SWAPPED (bank 1 to 2 and bank 2 to 1)

O2S11 800mV range
O2S21 0.00V

The fact that the values didn't change at all on my scanner when swapped indicates to me that the bank 2 O2 is outputting a legit value since the PCM for bank 1 is reading the same value, right? That should also mean that there are no vacuum leaks. Keep in mind that when I first started this truck, there were a lot of miswires that this PCM endured, so it could have gotten smoked… Any thoughts?