evilstuie

Hi All,

I'm chasing some electrical gremlins in my 0411PCM LS1 swap into an 85 TransAM and need some help with what I should be seeing on the O2 Sensor wiring.
These are using the flat black 4 pin O2s for Bank1 & 2 pre cat, no second sensors, and I have a wideband for tuning on left exhaust only.
When I log in HP tuners when the car fires up, my left o2 is sitting around 0.1v-0.3v and the Wideband is completely lean (20.0), the right side is sitting on 0.448v with a bit of a twitch but doesn't move. ( suspecting it could be dead)

Here's the thing though, the right side is nice and hot at the exhaust side, but the left side I can grab onto after a minute of the car running and it's only slightly warm, like it's not even firing.
I checked all the coil wiring and injectors for correct voltages, 12v where it should, ground on the coil pack, and about 430ohms on the control wires.

I got down to the O2 sensors and got these readings:

Left side:
Pin A: 4.4v
Pin B: 1.26v
Pin C: GND
Pin D: 12.4v

Right Side:
Pin A: 4.4v
Pin B: 1.26v
Pin C: 12.4v
Pin D: GND

I was told the heater pins C&D don't matter with polarity, but as far as I know Pin A is meant to be low reference so I was expecting something of a 0v / GND continuity situation and Pin B is High which I expected would be 1.0v.

Is anyone able to confirm what voltage should be outputted from the harness when the O2 sensor is unplugged?

G Atsma

Injectors showing voltage is normal even when not firing, as they activate by grounding. Voltage is live at all times.

evilstuie

Yeah sorry, I should have written that a little clearer, the voltage supply for both rails is there, and the "firing" grounds are connected. I was isolating the fuel supply as the issue for the left bank not warming up and firing.

evilstuie

no-one knows what the PCM is meant to output for the low and high O2 wires?

RC1

Since the O2 sensor is a Voltage generator, I don't believe you should see any V from the harness itself. When you check these voltages, what are using as your ground reference to your meter (black lead)?

evilstuie

I was using the chassis as the ground.
I'd assume the low signal should be 0v and high would be the 0-1v the o2 sensor generates, but neither of those are reading like that.

RC1

Are the voltages that you measured with or without the sensors connected?

RonSSNova

iTrader: (3)

[QUOTE=evilstuie;20428489

Is anyone able to confirm what voltage should be outputted from the harness when the O2 sensor is unplugged?[/QUOTE]

.448v is the bias the ecu provides. So this would tend to indicate a dead sensor.