P0141 code..help please.. - Maintenance and Repair Forum

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P0141 code..help please..
Saturday, March 19, 2016 2:13 PM
Ok so i have been dealing with this for a while now. When i first went under my car the wires for the harness on Bank 1 Sensor 2 were completely stripped and 1 of the 4 was ripped apart. I resealed them all and rewired the severed one. Placed a new O2 sensor on tailpipe and replaced fuse (Yes it was blown). I still get p0141.. I have attached a video that i sent to a friend who doesn't know either. Is there a way to test the 2 white wires? or the heater inside the O2? Brand is Ultra-Power. Please help me fix this problem so i can pass emissions >_<

https://youtu.be/UrP7xZyo6-Q <--- Video link of O2 Monitoring.

Re: P0141 code..help please..
Saturday, March 19, 2016 2:15 PM
forgot to put i have a 2002 cavalier 5spd 2.2.
Re: P0141 code..help please..
Wednesday, March 23, 2016 10:47 AM
Hi Alex,

I do not have an '02 Cav, mine is '05, with the ecotec engine, so I can only give generic comments. The service manual I have is specific to that '05 model.
It helps if you could find a wiring diagram for your car that shows the heater circuit.

The ox-sensor heater works with 12V. It gets +12V through a fuse, and the ECU gives the ground.
So when the ox-sensor is supposed to operate one of the heater lines should be on ground, the other should have +12V.
You could check these with a test light. Use a test light as it gives some load as well, unlike a DMM.

On Bosch sensors the heaters are white, both lines, there the polarity does not matter. For the sensor part the ground and the signal polarity matters, so that would be different colors. Again, on a Bosh sensor those are gray and black.
GM colors, or a different make sensor could be different, but the two same color wires on the sensor would be the heater line.

The fault reporting on the '05 (according to eBay it uses the same model sensor) is set if the heater current is less then 0.2A or more than 1.5A. This sets the hot heater resistance from 8.6 Ohm to 60 Ohm. My guess would be a working hot resistance around 10 - 20 Ohm or so. Cold heater resistance would be smaller. You could check the heater resistance in the sensor with an Ohm-meter of a DMM. The heater resistance would probably below 10 Ohms cold. Any resistance value significantly higher means probably a burned out heater, in that case you need a new sensor.

The fluctuating signal you see is a working ox-sensor, it is reporting on or off, the engine control algorithm is based on that, under- and over-compensating quickly.
The smooth ox-sensor signal is probably the one after the cat, there you do not get fluctuations, the cat removes the "fluctuations".

Hopefully all you have is some fault in your wiring.

Hope this helps, Peter
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