Removing / Reinstalling O2 Sensors

I try to remove the connector so that the wires do not twist.

 

I would believe if one was careful, and had enough slack it could work.

 

It's very easy to break wires by torquing them up in that fashion. The proper method is to disconnect the plug, then remove the sensor.

There is seldom enough slack in the wires to do this, and by twisting them together, you can easily disturb the connections to the O2 sensor bulb. I'd suggest replacing them now that they are an unknown quantity.

 

What car/model is this for? A friend of mine is going through same scenario now on his 430. Thanks.


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On my F355 spider I removed and installed them like your technician. I must have been lucky, no issues. Makes sense that twisting the wires, stranded or not, can cause breakage.

 

I always try to remove connectors, but that having been said this too puts wear on the pin/socket OD/ID interface and reduces the pin/socket retention force, both of which can lead to high contact resistance and later to intermittent connection and as bisel said leads to risk of breaking the connector.

I would in your case do some more diagnostics with your OBDII code reader, because your P0421 / P0431 trouble codes, related to the catalytic converter not reaching threshold temperature, indicate I think more a problem with the convertor, because the O2 sensors shouldn't influence the convertor reaching temp, or? I think there are separate codes for the O2 sensors themselves, one for bad sensors and one for "lazy" (slow-responding) sensors. And maybe even another for heated O2 sensors (heating circuit)

 

Not entirely true. The OBD2 code 0421 is detected using the signal of the rear O2 sensor compared to the signal of the front O2 sensor to "surmise" the efficiency of the cat converter. Not all OBD2 cars have thermal couple to decode the temp of the cats. So in this case, a bad rear O2 sensor or front O2 sensor will throw that code. Too bad because the sensors on the 360 is very expensive, being the wide band version.

 

Good discussions, and thanks for the correction!

 

Be sure to put some anti seize on them also. I had totally fused sensor on an old CAT when trying to install new CATS.

 

New Bosch O2 sensors will come with copper anti-seize applied. If reinstalling used ones, good advice to add a small dab to the threads.

 

It's amazing to me that it takes a team of engineers to develop and design a vehicle yet the bulk of 'mechanics' have little if any secondary education. Sure there are trade schools to learn various systems etc.. but the fundamentals of material science and engineering is absent. It's a wonder that vehicles stay together for as long as they do. The good mechanics I know have taken the time to learn those things and some actually have an engineering background, but they are rare. It's getting to where one needs a degree in computer science to sort a vehicle.

That said, the O2 sensor while a fairly basic item is subjected to a severe environment for prolonged periods of time. Twisting up the wires is just plain lazy. Aside from possible connection damage a heat cycled sensor with aged wires will form stress cracks, oxidation of the wires over time will lead to increased resistance esp if the wire become damaged from physical abuse. Since the sensor operates with very low current signals fluctuating resistance will give false readings and out of spec readings to the ECU. There's a lot more that could be covered on why it's a bad idea to twist up the wires, though I leave that for another time. Long story short.. don't twist the wires, it'll potentially damage a new sensor and will damage an older one in lots of different ways causing odd readings.

 

That is the height of laziness. Post the name of the shop so they can be avoided.

 

When I replaced the O2 sensors on my 360 I knew they were bad and I already decided I will replace them both so I just cut the wires.

But being an electrical engineer by trade I strongly advise against twisting any wires as either the wires will pull out of the connector pins / sockets or the wire strands will break giving an intermittent connection.

Dan