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.

evilstuie

Did you ever figure this out?

Jordan Baca

I am having the exact same issue. Was it the pcm?

evilstuie

I ended up fixing mine by bypassing the wiring harness completely.

I ran new wires from all 4 points on each connector and ran them direct to the pcm for hi/lo signal, 12v accessory for the heater wire and ground and this solved the issue.

That was on a factory harness too, so not sure if someone had done something dogey or if the harnesses are just prone to a short somewhere but that solved it for me.

From memory when I tested the connectors originally they still had voltages and ohms but they might have had a weak grounding causing it to fail.

Just give up trying to find the problem and solve the problem with new wiring, that's my advice.

rworcester

My solution was to ignore it, go with open loop fuel tables, and then ultimately swap to a holley ECU

evilstuie

Good call.
$2 worth of wire or a few grand on a new setup and tune.

rworcester

Right. The only possible reason I went aftermarket ecu was to find a solution to my o2 sensor problem.

evilstuie

The guy is asking for a viable solution to his problem, not for a shitpost gloat about your Holley ECU.

rworcester

You realize this is my thread from 3 years ago, right? And I already told him I didn't find a solution, that I just dealt with the faulty sensor? Not sure why me buying an ecu 3 years after I had this issue is a **** post brag but OK

G Atsma

Evilstuie- Read the above again. Then go have something cool to drink...

Jordan Baca

Thanks! I’ll try re-wiring and see how it goes. I don’t understand the reason it’s doing this and am up for option that works.