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?

 

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

 

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.

 

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

 

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)?

 

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.

 

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

 

[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.