rworcester

I went the closed loop route on my turbo build to try and maintain some ease of driving for the street. When all was said and done, my bank 1 sensor reads correctly, but my bank 2 sensor stays constant at 450 mV. When I go into my VCM Scanner and force closed loop, bank 1 begins switching like it should and bank 2 stays "dead". We swapped the sensors side to side and the problem stayed on Bank 2.

We have ohm'ed out all wires and they go to the correct pins on the stock 411 PCM, and then we started checking voltage in the run position to make sure they're getting the correct values. Bank 1 had 12 V on the pink wire and 0.45 V on the purple high reference wire. However, Bank 2 sensor had 12 V on pink and 5 V on the purple high reference wire.

Shouldn't that be seeing around 0.45 V as well? The high voltage might be what is forcing the "dead" signal at the O2 sensor, and I am leaning towards it being a PCM issue. Other than that, the car doesn't show any other signs of a bad PCM.

jimmyblue

iTrader: (11)

Look for signs that the PCM has faulted the sensor
and jammed the input to center. I've seen this, though
some folks disagree that it's a deliberate PCM behavior.
Immature O2 activity / heater codes, or maybe a
"no MIL" rather than "no error reported" style of
"turning off codes". Might clear all codes and see if
anything wakes up. Also measuring voltage on wires
with a DMM is going to just average switching activity
so your bouncing B1 sensor seems right, CL tries to
make average sit where your switchpoint vs airflow
mode table says; B2 seems jammed high, for some
reason (like the fault behavior). And if it is faulted
it won't go away until you clear the fault or it clears
itself through enough drive cycles.

Now you say you beeped out all the wires, but I have
cut the wrong purple wire once... since this sounds
like a custom wiring job, you might just want to hand
chase that particular one and see that it isn't really
PCM5V and the real O2 sensor output isn't stuck to
something else.

rworcester

So I've ruled out the faulty PCM option. I grabbed a stock 0411 PCM from the junkyard, plugged it in, and the B2S1 still had 4.5 V on the purple wire while B1S1 had the correct .45 V. We also checked for continuity between the purple wire and all other wires to see if there was a short somewhere between wires giving us a wrong voltage, but there were none. If anyone has any other ideas I'm open for anything. This is the last thing really before I can go drive it around without a laptop open in the passenger seat.