O2 sensors don't work after 0411 swap L31 Vortec

[MrOverCast]

Hi guys!

So I did the 0411 swap on my 98 L31 Vortec a couple months back and recently I started the engine for the first time. The engine ran like absolute trash at idle, Would barely even start. While monitoring data with torque pro I come to find out my O2 sensors are flat-lined.....450mv (NO CATS) even at full operating temperature. PCM logger says its in closed loop if that helps. I understand the differences in isolated ground O2's and Case ground. I believe my harness is for isolated ground. (flat black 4 pin connector). Someone said the o2 sensors get their grounds from the pcm and that I would have to move some wires to a spot that provides a ground on there. Does anybody know how to fix this issue? im really stuck here

 

[Supercharged111]

I'd start by verifying every single wire in the PCM.

 

[MrOverCast]

I'd start by verifying every single wire in the PCM.

Did that every wire is good

 

[BNielsen]

Did that every wire is good

Check 'em again. Cross check which fuses power them, I had a MAF issue with my truck after my 0411 swap and it wound up being a blown fuse. In going through my harness twice I found 2 or 3 pins I had misplaced.
Could also be a damaged power wire for them? These wires don't get any stronger over the years, and they're brittle asf to begin with.

 

[MrOverCast]

Check 'em again. Cross check which fuses power them, I had a MAF issue with my truck after my 0411 swap and it wound up being a blown fuse. In going through my harness twice I found 2 or 3 pins I had misplaced.
Could also be a damaged power wire for them? These wires don't get any stronger over the years, and they're brittle asf to begin with.

Ill try to check them again. The heater works on the O2 but not the signal

 

[L31MaxExpress]

Hi guys!

So I did the 0411 swap on my 98 L31 Vortec a couple months back and recently I started the engine for the first time. The engine ran like absolute trash at idle, Would barely even start. While monitoring data with torque pro I come to find out my O2 sensors are flat-lined.....450mv (NO CATS) even at full operating temperature. PCM logger says its in closed loop if that helps. I understand the differences in isolated ground O2's and Case ground. I believe my harness is for isolated ground. (flat black 4 pin connector). Someone said the o2 sensors get their grounds from the pcm and that I would have to move some wires to a spot that provides a ground on there. Does anybody know how to fix this issue? im really stuck here

Signal grounds only on the PCM side. Heater circuits have an external ground. Are all 4 02 sensors still in place or only 2? I find it difficult to believe a broken wire or single pin out of place would kill 2 to 4 02 sensor signals. Maybe the PCM was tuned open loop?

 

[MrOverCast]

Signal grounds only on the PCM side. Heater circuits have an external ground. Are all 4 02 sensors still in place or only 2? I find it difficult to believe a broken wire or single pin out of place would kill 2 to 4 02 sensor signals. Maybe the PCM was tuned open loop?

I only have the pre cat 02s hooked up and I also have a dual exhaust. The tune is a stock 2002 express van. The whole engine and wiring harness was pulled from another vehicle and is now in my squarebody chevy. I bought new rock auto NTK O2s sensors and couldn't get it to work. this is my second set of O2 sensors. I also double checked the pinout for both 02 sensors but no luck.

 

[L31MaxExpress]

I only have the pre cat 02s hooked up and I also have a dual exhaust. The tune is a stock 2002 express van. The whole engine and wiring harness was pulled from another vehicle and is now in my squarebody chevy. I bought new rock auto NTK O2s sensors and couldn't get it to work. this is my second set of O2 sensors. I also double checked the pinout for both 02 sensors but no luck.

I know this may sound dumb, any chance you confused Sensor 1 and Sensor 2. Should be using Bank 1 & 2 Sensor 1. Nothing on Sensor 2. My 97 van has the stock 02 sensor wiring with both the 0411 and P59. Just repinned. My 99 Tahoe also has the stock 02 sensor wiring on the 8.1L with a P59.

 

[MrOverCast]

I know this may sound dumb, any chance you confused Sensor 1 and Sensor 2. Should be using Bank 1 & 2 Sensor 1. Nothing on Sensor 2. My 97 van has the stock 02 sensor wiring with both the 0411 and P59. Just repinned. My 99 Tahoe also has the stock 02 sensor wiring on the 8.1L with a P59.

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Sorry Not trying to be dumb But these are the two im using. (Circled in red.)
Like I mentioned before im not using 1, and 2, in the pic.


This is the style connector the pre cat o2s use and thats what im currently using. (Not that specific o2 in the pic)

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[Supercharged111]

This is beginning to sound more like an issue with the powetrain swap into the square body than the 411 itself. May be better to look at it from that perspective.