Relek37

Got A P0125 Cel a few days ago on my 2000 4runner, now I think my O2 sensor has failed, I have ordered a new one. Prior to this happening I was getting a P0171 Cel, that made me think my O2 sensor was getting weak.
I Crawled under the truck to see what is involved in the replacement of the sensor. The removal of the sensor looks straight forward but the wires go up under the tranny and I cant get a good grip on the plug to unplug it. Does
anyone know a trick on how to unplug the O2 sensor? Thanks

Pozi

Hello and wecome to YT.

Hold off before you replace the sensor(s). You need to troubleshoot the conditions. There may be a short even though both those codes point towards the o2 sensors. Give me a PM with an email address and I will email you the FSM troubleshooting guides for those codes.

silver2000runner

“Please assist if possible...
I had my clutch changed on my 2000 4x4 3.4L 5spMan 4runner SR5 and upon picking the car up found MIL - code p0125 - that would not clear. I ****ed around with coolant system research and sensor repairs for several months never correcting it and I got lazy - accepting the 2mpg loss of efficiency.

Now I can't pass inspection with the light on and it's got to get fixed.

I found that my clutch mechanic must have damaged the wiring harness on O2 sensor B1S1. Looking under the vehicle I found one of the 4 wires to B1S1 sensor connection broken. I soldered this back together - cleared the code - code reappeared.

I have confirmed 0.0 volts on B1S1.
I have switched O2 sensor locations on the car to see if the 0.0vdc measurement would move to B1S2 (indicating a bad sensor).
ODBII scanner still indicated 0.0vdc on B1S1, indicating open or short still occuring on B1S1 harness or connector.

This pointed me back to the known damage to wiring harness found following clutch change.
I tested each of the B1S1 connector wires for continuity through the damaged/repaired section of the harness. All good !!! ???

I have not tried to measure any voltage on the connector with the car running (heater voltage, gnd, closed loop control voltage). I suppose that would be my next step.

Am I on the right track or is there something easy that I am missing?
Is my ECM blown?
How can I test my ECM to know without buying a replacement?

silver2000runner

Please assist if possible...
I had my clutch changed on my 2000 4x4 3.4L 5spMan 4runner SR5 and upon picking the car up found MIL - code p0125 - that would not clear. I ****ed around with coolant system research and sensor repairs for several months and got lazy - accepting the 2mpg loss of efficiency.

Now I can't pass inspection with the light on and it's got to get fixed.

I found that my clutch mechanic must have damaged the wiring harness on O2 sensor B1S1. Looking under the vehicle I found one of the 4 wires to B1S1 sensor connection broken. I soldered this back together - cleared the code - code reappeared.

I have confirmed 0.0 volts on B1S1.
I have switched O2 sensor locations on the car to see if the 0.0vdc measurement would move to B1S2 (indicating a bad sensor).
ODBII scanner still indicated 0.0vdc on B1S1, indicating open or short still occuring on B1S1 harness or connector.

This pointed me back to the known damage to wiring harness found following clutch change.
I tested each of the B1S1 connector wires for continuity through the damaged/repaired section of the harness. All good !!! ???

I have not tried to measure any voltage on the connector with the car running (heater voltage, gnd, closed loop control voltage). I suppose that would be my next step.

Am I on the right track or is there something easy that I am missing?
Is my ECM blown?
How can I test my ECM to know without buying a replacement?