pcmhacking.net

You used a VS wiring loom?

The VS ecotec had issues with the O2 sensors with one bank not reading correctly due to an earthing issue (the sensor and heater had an earth bond). This could be similar to what your issue is. The cheap fix was the cut the heater wire on the suspect O2 sensor, the proper fix was to separate and re-wire the earths.

yeah there was plenty of info on the net as to how to fix it from memory.

I linked both O2 earths a while back. Then both to another earth ... I posted something about that in a different thread.

Checking my notes it was, Link D14 & D16 and also A2 together

Still I do agree that there could be a wiring explanation, a phantom fault.

Thanks for the suggestions non the less.

That said , its easy to disable both heaters at the 6pin plug near the fuse box (I had to add a power feed when I modified the VP Battery/Relay loom)

Worth trying to remove a load from the grounds.....hmmm

Looking at that picture the issue is the earth bond between D15 and A2 for the LH sensor signal. I think someone fucked up as I could swear that the bond should have been between D16 and A2 as it would then have replicated exactly how the RH sensor is wired.

I don't think linking D14 and D16 with A2 would solve the issue (because you can still get signal contamination at the bond with A15).

wtf..... in that picture they have bridged the LH o2 sensor signal (D15) direct to earth. thats never going to work! are the cars really wired like that or was it a fuck up in the drawing?

There was a genuine issue with the O2 sensors giving false readings on the VS ecotecs. One must assume that the drawing is indeed how it is wired. I don't know if anybody has ever actually stripped out a loom to confirm if the drawing is 100% accurate but the issue certainly was.

wow, that is messed up. Shorting the o2 straight to ground lol

Well, To be fair- if it was wired like that it couldn't work at all.

But it raises questions, the error I have is an average of 100mV. Enough to throw the ecu by 20% apparently.

Fresh investigations tomorrow,

Disable O2 heaters for a logging run after warmup. Taking them out of circuit.
Revisit the earthing for the sensor vs heater gnds if anything shows up.

Cheers

-sean

Nuffin...

That diagram also has the pin labeling wrong for the O2 sensors (ABCD)

B & C are swapped.

Useless grunts in the drawing office.
.....

Anyway, I de-pinned the heater grounds from the sensors. They take now about a minute to warm up and get online.

And nothing has changed. RH LTFT still wanders off deeply negative.
I'll pull the rocker covers off and check valve function... trying to imagine a scenarios where lack of air to a cylinder is causing a rich condition.

Cheers.

what about disabling closed loop and reset blm's, then use a heat beam gun to check each exhaust port temp to at least narrow it down to a particular cylinder?