Hi All,

I have a 0411 24x project car that has an LS1 wiring harness from a Holden VxII LS1 commodore and has been thrown into a 85 TransAM.

Everything else is working, and the car will start, run and drive but it is having horrible hesitation, backfiring and stuttering issues, and the tuner can't seem to get rid of them.

He dialled the fuel in with the wideband but couldn't figure out the rest.
I've loaded a bunch of different spark tables to try and get something near my motor (400SBC, 270HR CAM, AFR heads, 28lb LS1 injectors) but nothing helps.

Anyway, enough background, I've tried everything else and am now back at the O2 sensors.

When I run the scanner it shows left bank o2 moving about from 0.400v - 0.900v as expected, but the right bank O2 sensor just sits between 0.445-0.450v.

I went under the car and tested the harness wires, and it got even stranger.
I have from left to right on the connector:
4.4v
1.2v
nothing
GND @0.1 ohm

This is while the car is powered. I thought GREAT!, this is the problem until I checked the working drivers side and found the same voltages. (while ignition is on and confirmed while car is running)

From what I've read, I should have a High reference, Low reference, 12v & GND, and I have pretty much none of these.

Before I go pulling wires or bypassing the harness can anyone confirm:

*What voltages I should see from the harness going to the o2 sensor?
*What pins comes from the PCM, and what have 12v/GND?
*Are these different for different sensors/calibrations?

Could this be the primary cause of my problems or is this the way the o2 sensors are meant to work?
It seems strange that with identical setups on each side the scanner would see different results. I've also tried using AVT-852 and ELM327 scanners and get the same results.

 

no-one?

 

Data logs?

 

are you using both front O2 sensors or the rears from the harness?

 

O2 sensors get a 12v supply directly from the fuse panel.

 

https://drive.google.com/file/d/1jKw...ew?usp=sharing

You just need to add the file extension ".lgf" to the end of the file name.

Logged using DashCommand and you can view the files with ScanXL for free.

 

Front only, harness is from a VXII LS1 Holden commodore, they didn't have post CAT sensors.

 

This is a custom job with custom harness into a 85 TransAM and the fuse panel I'm using doesn't have a specific fuse for O2 heater power.

I'm going to trace the wire as I suspect with 4.4v it's getting power from the BCM and may need a relay somewhere in between to give it 12v instead of direct wire-up.

 

So I found the wire to put 12v to the heater. But here's the funny thing, when both o2 sensors are unplugged, there's no continuity between the wire and ground.
When I check resistance between the pin on the plug and the wire end in the harness i get 8 ohms resistance. When I put 12volts through the wire end and measure it at the connector pin, there's 0v... what the hell?