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

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?

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

hi, i kinda had a similar issue after getting mine running, ultamately it was solved by a good tune. i would suggest getting a good tuner (finding one is hard) i do have the name of the place that did mine & i have not had any issues since... 8100 miles now.
hope this helps good luck!

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

I would post the same post over on LS1tech.com.

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

Thanks, I give that a try!

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

agree try LS1tech.... there are a few sub cat. that might apply. (conversions & swaps) and the programming catagory. again good luck.

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

PROBLEM RESOLVED!

I went back and forth with Brendan at lt1swap.com (Brendan programs my PCMs) and he told me how to determine if it was a wiring or PCM issue. Needless to say, the PCM was smoked. I swapped in another PCM and the O2 voltages on both banks are now good and the short term and long term fuel trims are normal.

This is what he told me to do:

Unplug O2 on bank 2 with KOEO.
- O2S21 should be 0.450V

My result was still 0.000V, so the next step was to remove pins 26 and 66 from the blue connector
- O2S21 should be 0.450V

My result was still 0.000V. Had it been 0.450V, then root cause would’ve been a wiring issue of some sort. Based on my result, Brendan stated it was likely my PCM, which it was.

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

glad you got the issue found & fixed. I had a similar issue with the temp reading of the truck, long story... ,but after ALOT!! of back and forth with many shops, techs & mechanics, it ultimately was a mech failure of the W.P. everything was pointing towards a bad ECM....