# What could cause both upstream sensors to NOT fluctuate? **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [August 24, 2019, 9:13pm UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404 "2019-08-24T21:13:06Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![sarvesh.bathija\_156605](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/sarvesh.bathija_156605/32/17247_2.png) [@sarvesh.bathija\_156605](https://community.cartalk.com/u/sarvesh.bathija_156605)\ **Post date:** [August 24, 2019, 9:13pm UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/1 "2019-08-24T21:13:06Z")
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? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [August 24, 2019, 9:16pm UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/2 "2019-08-24T21:16:41Z")
That’s called lazy O2 sensors. Or in other words, the O2 sensors aren’t switching. > **[Sensors: When to Replace Them | KnowYourParts](https://www.knowyourparts.com/technical-resources/electrical/sensors-and-when-to-replace-them/)** > > Automotive Sensors provide input for the Powertrain Control Module (PCM) which makes the critical control decisions. Tester ---
**Author:** ![sarvesh.bathija\_156605](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/sarvesh.bathija_156605/32/17247_2.png) [@sarvesh.bathija\_156605](https://community.cartalk.com/u/sarvesh.bathija_156605)\ **Post date:** [August 24, 2019, 9:18pm UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/3 "2019-08-24T21:18:37Z")
Thanks @Tester. IN my case both have been replaced, twice! Are theire any reasons for them to be…lazy? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [August 24, 2019, 9:24pm UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/4 "2019-08-24T21:24:24Z")
Contamination from some source. Did you read the article I attached? Tester ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [August 24, 2019, 9:34pm UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/5 "2019-08-24T21:34:58Z")
You’re vehicle has wide band O2 sensors. To understand how these function, read this. > **[Wideband Oxygen Sensors Vs. Narrowband: Understanding The Differences](https://www.brakeandfrontend.com/wideband-oxygen-sensors-vs-narrowband-understanding-the-differences/)** > > Wideband air/fuel oxygen sensors may appear similar to conventional narrowband oxygen sensors, but there are quite a few differences that you need to be aware of to service vehicles with this new style sensor. Tester ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [August 25, 2019, 1:07am UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/6 "2019-08-25T01:07:31Z")
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. ---
**Author:** ![sarvesh.bathija\_156605](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/sarvesh.bathija_156605/32/17247_2.png) [@sarvesh.bathija\_156605](https://community.cartalk.com/u/sarvesh.bathija_156605)\ **Post date:** [August 25, 2019, 1:26am UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/7 "2019-08-25T01:26:09Z")
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. [https://community.cartalk.com/t/2006-nissan-altima-v6-random-misfire-and-high-fuel-trim-big-headache-will-buy-beer/147334/4](https://community.cartalk.com/t/2006-nissan-altima-v6-random-misfire-and-high-fuel-trim-big-headache-will-buy-beer/147334/4) ---
**Author:** ![tcmichnorth](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tcmichnorth/32/25126_2.png) [@tcmichnorth](https://community.cartalk.com/u/tcmichnorth)\ **Post date:** [August 25, 2019, 2:35am UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/8 "2019-08-25T02:35:02Z")
Thanks for the site reference. I was going to ask about this, as they are becoming quite popular. ---
**Author:** ![sarvesh.bathija\_156605](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/sarvesh.bathija_156605/32/17247_2.png) [@sarvesh.bathija\_156605](https://community.cartalk.com/u/sarvesh.bathija_156605)\ **Post date:** [August 26, 2019, 10:57pm UTC](https://community.cartalk.com/t/what-could-cause-both-upstream-sensors-to-not-fluctuate/147404/9 "2019-08-26T22:57:44Z")
@Tester took me a while but I understand what you mean now by wideband. Thanks for the answer!