P0141 CEL still on after replacing O2 Sensor

Using the diagram I uploaded..

On your B1S2 there are 4 wires, 2 are the same color. These should be the heater circuit. Unplugged and cold, the resistance should 11 to 16 ohms across the heater circuit The TOTAL resistance with the o2 Sensor plugged in and measured from the PCM HT2 (Red / Green for manual trans) to a good ground should be pretty close to what the o2 sensor by itself is.

The W/R (pin 2) on the harness that goes to the O2 sensor should have +12v with the truck running... key on there shouldnt be voltage present. If there was voltage and you sat with the key on for a minute before you start the truck it wont run correct... cold motor, warm O2 sensor.

The PCM is looking for total resistance in the heater circuit.

 

That's the thing! Ground is good, and I'm getting voltage on W-R and R-W.

 

I found a 2001 wiring manual, but they are pretty much the same thing. Mine says HTS instead of HT2 and there is no difference between M/T or A/T for the HTS wire. Sorry for not telling you that.

I understand that the two wires with the same color (black) are the wires to the heater on the actual O2 sensor.

Yes, the TOTAL resistance is only 0.1 ohm greater than the actual sensor heater resistance, so that is good.

I have voltage on pin 2 of the O2 sensor harness (W-R) with key on and truck not running.

 

It would be hard for me to accept and I would double and triple and quadruple check my tests, but it looks like ECU is defective if that circuit is functioning correctly but still throws the MIL for that code.

 

Checked over my tests again, everything still looks good.

I think I am just going to settle with this for now and ignore the light. Doesn't really have any actual impact on the truck's performance, so I am not going to try find a used ECM (they're not cheap!) at this time.

Thank you everyone for the input.