Ferocity02

iTrader: (60)

I just put my truck back to stock other than a 4L80E instead of the 4L60E. I put in brand new Bosch rear O2 sensors. I'm getting codes P0140 and P0160 for no activity for the rear O2 sensors. When I log with EFILive, these sensors are flatlined at ~450 mV +/- 5 mV... no real activity whatsoever. It's basically like the sensors are unplugged.... I unplugged a front sensor and it also shows ~450 mV.

I bought another O2 sensor, same thing. The heaters in the sensors work great. I bench tested one sensor and I think it's working fine, responds to fresh air vs. gasoline-rich air.

I did continuity tests on the tan and purple signal wires that go to the PCM and they are fine and do not appear to be shorted to any other wires going to the PCM or ground. The wires are physically in tact, no melting or anything of that sort.

I am using a stock tune flashed into the PCM with nothing but a 4L80E trans segment that has been modified slightly for gearing. The engine calibrations are all stock other than a handful of transmission related DTC enablers that were changed. The DTC enablers for the rear O2 sensors are all stock... "2 trips, emissions related."

Anyone have any ideas? I am at a total loss here.

Ferocity02

iTrader: (60)

Anyone have any thoughts? Still scratching my head on this one. I flashed in a 100% stock tune and no change.

Mongoose350

iTrader: (1)

Is there any possible breaks in the harness? Should just tune them out, they aren't really needed anyway.

Ferocity02

iTrader: (60)

I'm putting the truck back to stock and want everything to be working before I sell it.

Wiring seems good. The two signal wires to the PCM (purple and tan) have continuity between the sensor and the PCM and don't seem to be shorted to any other wires or ground.

Ferocity02

iTrader: (60)

Welp... I figured it out. Turns out the 2 sensors I got on eBay were bad. When I bought the 3rd sensor at Autozone and tested it, I neglected to ground the sensors case to the exhaust. It works fine once the case is grounded. The sensors I got online are the same as the one I got locally, albeit without the boxes and half the price. Maybe they were fakes.

Hopefully I can return the O2 sensors even though I installed them. If not, I'm going to file a complaint with PayPal.