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

[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?

 

[TotalyHucked]

Did you get the injectors flowed and checked before install? Could have one or more hung open/dribbling when they shouldn't be firing.

Also, throw that intake in the trash. Those are the worst possible things you could put on one of these engines. They lose all low end torque, they make weird sounds back through them and half the time they're warped/won't seal. Also don't use starter fluid to check for vacuum leaks cuz that ****'s hard on the motor, just use brake clean.

What are you using to watch real time data? Has it been tuned for the new combo or did you just throw it in with a VATS delete?

 

[shortboxin]

As for the injectors, not flow checked, but if they were leaky I wouldn't get a lean condition, would I?

Not building a performance truck, it's bone stock and it's going to stay that way. Just wanted something that looks better than the ugly plastic factory intake and didn't want to spend $1k for one. Also, truck's got 3.73 gears and it still lights them up with this intake. Do you have an intake recommendation that's $500 or less that's not a piece of crap? Besides, if the intake was warped, wouldn't I be getting a lean condition on bank 1 when I plugged the bank 2 O2 into the bank 1 PCM connector?

Using an Actron unit from about 10 years ago to read data. No, it's not tuned for the intake, but that doesn't explain bank 1 working and bank 2 running lean.

 

[TotalyHucked]

You're right, leaking/hung open would be rich. But you could have one or more not firing enough (they're obviously still firing if you're getting temp in each cylinder). My temps at the primaries just out of the cylinders are usually 300+ degrees though, even long before operating temp. 180 is cold.

Intake wise, the stock ones are the best you can run. Stock truck or you can go to the junkyard and grab an '08-up 5.3 intake and it's the TBSS style with the bigger throttle body. Grab it complete with injectors and all (and get those flowed) cuz those injectors are bigger, like 30-36lb/hr instead of the 24lb/hr the 4.8s probably are.

What I mean by the tune is, has a custom tune been written for your whole setup? With the correct injector sizing/flow data and everything? Or is it a factory tune just with the VATS turned off so it'll run? If it's not tuned, it's going to run like crap and you're going to see weird fueling and get weird codes until it gets tuned properly.

 

[Ricko1966]

Did you get the injectors flowed and checked before install? Could have one or more hung open/dribbling when they shouldn't be firing.

Also, throw that intake in the trash. Those are the worst possible things you could put on one of these engines. They lose all low end torque, they make weird sounds back through them and half the time they're warped/won't seal. Also don't use starter fluid to check for vacuum leaks cuz that ****'s hard on the motor, just use brake clean.

What are you using to watch real time data? Has it been tuned for the new combo or did you just throw it in with a VATS delete?

Don't use brake clean confirming vacuum leaks. Burnt brake clean is phosgene gas. Not all brake cleaners,but some so just get in the habit of not doing it for safety sake. Use carb cleaner,intake cleaner,oil,or propane.

 

[Ricko1966]

A lean code and smells rich could be an ignition miss. You smell the unburnt fuel,the oxygen sensor sees the 14 parts unburned air.

 

[shortboxin]

A lean code and smells rich could be an ignition miss. You smell the unburnt fuel,the oxygen sensor sees the 14 parts unburned air.

I hear you, but I'm not getting a miss code, so maybe the PCM just isn't detecting it? I'm just not understanding the 0.00V on my upstream O2 on bank 2.

 

[shortboxin]

What I mean by the tune is, has a custom tune been written for your whole setup? With the correct injector sizing/flow data and everything? Or is it a factory tune just with the VATS turned off so it'll run? If it's not tuned, it's going to run like crap and you're going to see weird fueling and get weird codes until it gets tuned properly.

I figured that's what you meant. When I sent the PCM to Brendan, he was given all the specs for the engine including injector part numbers. I would guess that he's loading a factory tune and turning VATs off, so technically it's not tuned. I did not run into this on my last LS swap and he took care of that one as well. I've never swapped an intake on an LS before though.

 

[Fat 454]

Burnt brake clean is phosgene gas. Not all brake cleaners,but some so just get in the habit of not doing it for safety sake. Use carb cleaner,intake cleaner,oil,or propane.

as made infamous by both the Axis and Allies, during the trench warfare of WWI ..

 

[Camar068]

After flaming up the engine compartment on a 99 durango using wd-40, I now use starter fluid lol.

Watching as I have both banks lean on my swap.

 

[Camar068]

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:

from experience with the O2 sensors (Thank you GM for the purple wire on one and purple/wht on the other.....and grease and grime...easy to get backwards), it will run like sh|t at idle at a light if they are backwards.....you have to give it gas while holding the brake to keep it running. A good take off from the lights, I think it ignores the o2's because when I took off it ran awesome.

Sounds like wiring to your 02 sensor on that bank to me.

[edit] after swapping did you reset the pcm and then start it. swapping them should make it idle like crap because it's reading one bank and it's adjusting the other (with my mishap above).

 

[Camar068]

probably a GND on that portion of the harness.

 

[hip2bsquare]

i had same issue after getting my swap running (2013 genIV 5.3 DOD in '86 C10) i had the injectors "tuned" and matched?? it did not help (initially) the only thing that fixed it for me (as suggested by huck) was to get a "custom" tune. the tuner i used worked about 3 hrs on it to adjust everything so the engine was happy. my suggestion would be to bite the bullet & get a tune made for it. if you desire i can give you the shop info. that did mine (yes i would recommend them) reasonably priced. hope this helps.... good luck

 

[shortboxin]

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.