Never use dielectric grease on O2 sensor electrical connectors

[koda2000]

Two things I recently learned about O2 sensors and how they work.

1) An O2 sensor needs an open path to atmosphere. It needs this external oxygen source to be able to use as a reference. It draws in external O2 through its wiring jacket and electrical connector. If you pack your O2's electrical connector with dielectric grease the sensor can not sample any external O2 and has nothing to compare what it's reading to. This will result in erroneous data being sent back to the PCM, which will adversely effect fuel trims.

2) O2 sensors do not require power to operate (other than for 4-wire heated O2 sensors). Once they heat up they actually generate the own electricity.

This was all news to me and I typically do pack my electrical connectors with dielectric grease. Interesting. Learn something new every day.

 

[donalds]

I heard the same thing but I was told it only apples to wideband type sensors on newer cars

But your info is probably better than mine

 

[96eb96]

Two things I recently learned about O2 sensors and how they work.

1) An O2 sensor needs an open path to atmosphere. It needs this external oxygen source to be able to use as a reference. It draws in external O2 through its wiring jacket and electrical connector. If you pack your O2's electrical connector with dielectric grease the sensor can not sample any external O2 and has nothing to compare what it's reading to. This will result in erroneous data being sent back to the PCM, which will adversely effect fuel trims.

2) O2 sensors do not require power to operate (other than for 4-wire heated O2 sensors). Once they heat up they actually generate the own electricity.

This was all news to me and I typically do pack my electrical connectors with dielectric grease. Interesting. Learn something new every day.

Silicon contaminates o2 sensors. That why bad head gaskets usually ruin o2 sensors. Even RTV has to say "sensor safe" e.g. it does not contain any Si.

 

[koda2000]

I heard the same thing but I was told it only apples to wideband type sensors on newer cars

But your info is probably better than mine

That's the info I got and the guy was not talking about wide-band O2 sensors. (IDK what the term for non wide-band O2 sensors is) The guy also has another video on how wide-band O2 sensors work, but I haven't watched that one yet. I just never gave much thought to how O2 sensors work so I found it very informative.

 

[J_C]

??? I must be misunderstanding what you mean, but on our 02 sensors, there is no problem with putting dielectric grease into the connector, which is not designed as direct contacts on the back of the sensor but rather pre-attached with wire. The grease should never touch the body of the sensor itself. There is nothing (no air) drawn through that wire, just standard wires to carry electricity.

Can we get a link to that video?

 

[koda2000]

??? I must be misunderstanding what you mean, but on our 02 sensors, there is no problem with putting dielectric grease into the connector, which is not designed as direct contacts on the back of the sensor but rather pre-attached with wire. The grease should never touch the body of the sensor itself. There is nothing (no air) drawn through that wire, just standard wires to carry electricity.

Can we get a link to that video?

I'll see if I can find the video and include link.

I couldn't find the video that had watched, but the below link also talks about air needing to get into the O2 sensor.

 

[J_C]

Whoever made that video, I want some of what they were smoking. It is baffling that someone went to the trouble to make that video and added that misinformation. I suppose it is a sign of the times, that anyone can set up an account and present mostly true info, then if they are wrong about something, it is easy to assume it is an authoritative source when it is not, rather just some guy trying to extend his knowledge past its limits to make a buck as a youtube channel.

There is no reason why it would be designed to suck air through the length of the cable sheath, rather it'd have a dedicated tube for a precise/dependable flow, and couldn't even if an engineer wanted it to because the sheath does not extend all the way to the end of the sensor and make an air-tight seal against it.

The sensor having access to outside air through the back is certainly possible, and it might even suck that air around the wires going in at their point of entrance on the sensor, but it does not pull air through the cable itself. Here is a picture of a motorcraft sensor F88Z9F472CA (aka DY862) for my SOHC, notice that these are standard wires and the sheath does not go all the way to the sensor (which is typical), there's no way it's pulling air through it back to the connector.

Suppose that an engineer wanted to add an air tube to it for whatever reason, say to get that up out of the way of road moisture, then a 4 wire sensor would have a 5th wire-looking thing that was instead a hollow air tube, or for a 2 wire sensor a 3rd faux-wire-hollow-tube, and one fewer connector pins than it had wires, but that is stagnant air, would only serve as a vent for a pressure release. Nothing like that could ever be an active sampling method without a pump to exchange the air. Also if they didn't want it to have an air-tight seal, they wouldn't have put the o-ring seals in them.

 

[Hamster65]

Your info about the electrical connector is totally wrong. Dielectric grease serves 2 purposes.........keeps moisture out of the connector and provides a better electrical connection between mating pins. The connector has ZERO to do with what the O2 sensor senses or how it senses it. It's a very simple design and only reads what is travelling through the exhaust pipe. The ECU determines if the reading is correct based on a programmed set of parameters. Any "outside" air getting to the sensor would throw the measurement off and cause your engine to run poorly because, the ECU would try to compensate by adding more fuel to the air/fuel mix.

 

[RickOTR]

Never noticed any problems using dielectric grease on the o2 sensor connectors.

 

[MrQ]

Two things I recently learned about O2 sensors and how they work.

1) An O2 sensor needs an open path to atmosphere. It needs this external oxygen source to be able to use as a reference. It draws in external O2 through its wiring jacket and electrical connector. If you pack your O2's electrical connector with dielectric grease the sensor can not sample any external O2 and has nothing to compare what it's reading to. This will result in erroneous data being sent back to the PCM, which will adversely effect fuel trims.

2) O2 sensors do not require power to operate (other than for 4-wire heated O2 sensors). Once they heat up they actually generate the own electricity.

This was all news to me and I typically do pack my electrical connectors with dielectric grease. Interesting. Learn something new every day.

I just... really?

Ok, so let's just not believe everything we see or read on the internet shall we and apply it universally? Context is important.
This info is incorrect in as far as it applies to Explorer's as I have changed quite a few sensors and some of them even have the di-electric grease in them.

Some O2 sensors (titania) are resistance based and do not make their own voltage (see link below) versus zirconia sensors that do. Our Explorer's use zirconia sensors. Titania sensors MAY use a sampling tube like you described, but it's not very common.

Titania

http://www.tomco-inc.com/Tech_Tips/ttt20.pdf

Zirconia

Zirconia Oxygen Sensor Function – How they work?

Zirconia Oxygen Sensors from SST can be at times difficult to understand how they operate.This article tries to make it as easy to read and understand.

www.sstsensing.com

 

[Hakcyourengine]

Dielectric greases non-conductive there's also a silicone base silicone kills O2 sensors I understand you're saying not to use a lot in just under threads but why not use the proper grease dielectric greases made to withstand hi 300 to 500 degrees depending on the type. You need to use a nickel or copper Base anti-seize. Will the dielectric grease work probably 90% of the Confusion lies with most never sees compounds that are not copper and dialogic reason look exactly the same. But if there is a chance of failure why not use the proper Greece they have it at the parts counter usually in like a little ketchup package.

% of the time

 

[J_C]

^ Welcome to the forum!

I think something went wrong with your quote.

This topic is about putting silicone dielectric grease on the wire connector, not on the threads to the exhaust pipe.

When the connector was new, it should have had a completely sealing rubber gasket, but over 20+ years, that gasket may not seal so well, so adding silicone grease helps, and also makes it easier to slide the connector together because sometimes those gaskets are high friction, if the plastic is (hopefully) clean.

 

[J_C]

Silicon contaminates o2 sensors. That why bad head gaskets usually ruin o2 sensors. Even RTV has to say "sensor safe" e.g. it does not contain any Si.

That's not what makes RTV "sensor safe". Many sensor safe RTV sealants have silicone in them. What makes them sensor safe is that they are neutral cure instead of acid cure that most silicone caulking is. The acid (even the fumes from it, doesn't have to be direct contact) will degrade certain types of sensors and otherwise, corrode bare metal it's in contact with.

If you were to get too much of any substance on the sense end of an O2 sensor, it can foul it, whether silicone RTV, non-silicone sealant, anti-seize, or just burnt oil deposits from a worn engine.

 

[410Fortune]

Die electric grease does not conduct electricity!!!

too much of this stuff can hurt your electrical connections. It is to be used to keep
Moisture out not to completely fill the wiring plugs with.
I have seen waaaaay too much used cause problems especially with spark plug wires

 

[C420sailor]

The ol’ “if some is good, more is better”