Diode grease in O2 sensor connector?


I had a check engine light and my mechanic investigated. The problem was with an O2 sensor and on inspection found diode grease in the connector. Is there any reason a previous mechanic may have put this there? Where would it come from if not?

At this point they are recommending cleaning the connector and replacing the O2 sensor, then reset/recheck the CEL.

The car is a 2004 Chevy Aveo. Also, would it just be easier for me to replace the O2 sensor myself (friend offered to help replace it)? The estimate for the recommended work by the mechanic is around $380.

I don’t believe dielectric grease on the connector is your problem. It is used to insure good contact and reduce corrosion of the contacts. Its used on spark plugs, bulbs, etc. I think probably the O2 needs replacing is all.

Yeah just replace it. It isnt horribly difficult to do yourself.

These type of electrical connectors are either Deutch type connectors or Packard type connectors. These connectors are designed to withstand the environment they’re expose to.

No need to add any type of grease.


Despite the fact that Tester is right, many manufacturers use dielectric grease in their connectors anyway.

I really doubt a previous mechanic would have touched the O2 connector unless there was a problem with the sensor or exhaust work was done.
The grease was likely there from the factory.
I’ve worked in the electronics field for 40 years and never heard of “diode grease”.

@circuitsmith: little known fact but grease is a horrible conductor - a ‘semi’ conductor if you will. Diode grease is used to make diodes, transistor grease yields transistors, fat grease makes FETs, etc but bacon grease just gives you heartburn.

Seriously, I use dielectric grease on all connections, including the o2 sensor I replaced on the Tacoma two weeks ago. It had mating ends that met a rubber gasket but protecting contacts is cheap insurance.

I believe its “dielectric” grease, not “diode” grease. I don’t know what diode grease is. Can’t say I’ve ever seen it on circuit boards but if you pull the tail light bulb out of your car, it will have dielectric grease on it from the factory.

I’m quite familiar with dielectric grease, heatsink grease, elbow grease, nose grease (good for covering scratches on negatives) and palm grease (aka cash).