Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

What could cause both upstream sensors to NOT fluctuate?

I’m noticing my Bank 1 upstream sensor voltage is holding steady at about .3 V and my bank 2 to hold steady at around .6-.7V. No fluctuating at all in both. What are typical reasons for this?

That’s called lazy O2 sensors.

Or in other words, the O2 sensors aren’t switching.


Thanks @Tester. IN my case both have been replaced, twice! Are theire any reasons for them to be…lazy?

Contamination from some source.

Did you read the article I attached?


You’re vehicle has wide band O2 sensors.

To understand how these function, read this.


Is there a particular reason you are monitoring the signals of those two sensors? Or just out of curiosity? The reason I ask is b/c on your particular engine & emissions configuration this may be normal.

Hi @George_San_Jose1. I’m trying to track down a rough idle with random misfire code. Here’s a post which is related to the original issue. So I’m trying to find any sort of slight clue of what the issue could be.

Thanks for the site reference. I was going to ask about this, as they are becoming quite popular.

@Tester took me a while but I understand what you mean now by wideband. Thanks for the answer!