Bank 1 sensor 2 02 not getting much voltage.

I have an 01 tundra with the 4.7 and have been having trouble getting it to pass emissions. All my monitors are complete except my catalyst monitor. I have done the drive cycles pattern several times for the truck and nothing still. I looked at my 02 sensors to see if that was the issue and it made me more confused. When I first got the truck it had a check engine light on for all 4 o2 sensors. I replaced them all and they are seem to be working except for the bank 1 sensor 2 sensor. I swapped it with the one on the bank 2 side but still the bank 1 side showed very little to no voltage movement. It would either be 0 or .01 volts at idle. At driving speed the voltage would move a little bit higher but not much. My other sensor on bank 2 moves a little bit at idle and seems fine at speed. I'm not sure if there is something wrong in the wiring on bank 1 sensor 1 or if something else is the issue.

 

What brand of sensor did you buy, and where did you buy them from?

Is the wiring the factory-original wiring, or has someone spliced into the wiring at some point to install aftermarket sensors?

If you move the bank 1 sensors to bank 2, does the issue follow?

 

If you want to check for a short in the wiring, you could first identify the ground vs the voltage input for the O2 sensor. Next, take a 1.5 volt AA battery and a 10k ohm resistor and place the resistor between the 02 input and positive terminal of the battery. The negative terminal of the battery can be connected to the O2 ground connection.

Taking a volt or multi-meter, measure the voltage at the O2 input. If it’s still at or near ground voltage, you definitely have an issue with the wiring, otherwise if the input is 1-1.5 volts, you’re fine. Basically the O2 input should be relatively high impedance on the input and either rail at 1 volt which is the highest voltage produced by the O2 sensor or track with the input battery voltage of 1.5 volts. The 10k resistance will only allow micro amps to pass which could easily be clamped by a protection diode on the input circuit assuming its an IC. That would be my approach at least.

 

When I first got the codes for the downstream sensors i replaced them with some brand off of Amazon and those didn't seem to work right at all. They fit and clipped into the connector but the metal sensor end looked different and both had nearly any voltage fluctuation. As if they were both lazy. I got two other downstream sensors from trq and those are the ones still on the truck now. I don't see anywhere were someone would have messed with any of the wiring. And yes i've switched the sensors multiple times, but they all still show that bank 1 sensor 2 has practically no voltage and no fluctuation.

 

O2 sensors are one of a few parts you 100% want to buy Denso parts and DO NOT buy parts on scAmazon, fleaBay and WallyWorld. They're a known cesspool of counterfeits. I know it probably sounds absurd, but they DO NOT vet their inventory, and/or allow anyone to sell direct to the consumer with no protection. Either buy from a local store, Rock Auto, Summit Racing, any company that actually vets their inventory.

Did TRQ sell you Denso (OEM) sensors, or some other brand?

Did you only replace the downstream sensors, or all four, upstream and downstream?

What codes did you get that caused you to replace only the downstream sensors? Normally folks will replace upstream and downstream on the bank that failed, in pairs. Not just the downstream.

What codes are you currently getting?

Are you running the original catalytic converters on the truck?

 

Hey everyone I have a 04 tundra v6. I replaced upstream and downstream o2 sensors after it threw a code to replace downstream sensor. Since then, well idk if it’s since that actual time, however, my catalyst monitor will not complete its cycle. I’m trying to pass smog out here in lovely California but that one monitor just won’t complete and I’ve driven over 1000 miles since replacing…anyone have suggestions/help? Drive cycles, anything? Thanks

 

Did you use OEM (Toyota or Denso brand) sensors?

Where did you buy them?

Do you have a scanner that'll let you see whether you're open or closed loop?

 

I Used Denso, sorry thought I put that in the first message
I don’t know if the scanner shows me open or closed loop, how would I check that?

 

Basically the O2 sensors only start registering when the system enters closed loop and comes up to standard operating temp. You should've hit both within a thousand miles.

What scanner are you using? Does it allow you to see the output of each O2 sensor?

I've seen different scanners show different input/output. Like, here's an example from Noah's fun OL/CL debacle. His scanner shows loop state as "CL" and "OL" as I've just abbreviated: https://www.tundras.com/threads/crackhead-resurrection.94083/page-51#post-2555907

The reply just before the one I linked there shows O2 sensor output in his scanner.

I think Noah's issue he was working through ended up being a bad ground. But I don't think he had much more info from the mech friend of his who traced the wiring when Noah finally gave up. And he just had a kid, so I'm not about to text him and ask him to come here and give more info. If we can at least figure out which scanner you're using, we may be able to Google Fu and see what we find out.

But for now, that's where I would head with this. Confirm you can see all O2 sensors are on and registering normal readings. Then confirm if you're ever hitting closed loop, and if you're registering operating temp. I assume if one bank is ready and the other isn't, you must be... but that would leave another question ... why?!

 

Man thank you for the help! Here is the scanner I’m using, no idea what brand or anything, I’ll plug it in shortly when I have some time and see if I can check that

 

That’s a Henhaoro Chinesium scanner

 

Would this one be better? It says it checks o2 sensors as well as voltage

 

I honestly don't know when it comes to the budget Chinesium scanners on scAmazon. 80-90% of those under $50 are ultimately the same chips, same board, different LCD and case.

I personally prefer wireless OBDII dongles. Essentially, most act as nothing more than an interface/transmitter to your smartphone, and you can use a number of apps to link to that transmitter and get whatever info they're programmed to get. I'm currently using the OBDLink MX+ but it's a bit spendy (comes with a totally unlocked and pretty powerful smartphone app with lots of custom PIDs, though). Other folks like the BlueDriver units and similar.

Because your current unit doesn't have a ton of information on the web (it's pretty generic), I can't seem to strum up whether or not it can read individual O2 sensors and see closed/open loop status.

 

Ok got it thank you! Yea I’m ballin on a budget right now lol so just trying whatever I can for right now otherwise I don’t know what else to do

 

Had my truck for 20 years literally since 04, it’s been fine and passed smog every time and then all of the sudden this year it wants to be stubborn…

 

Ok so it looks like only one of my o2 sensors is getting voltage…

 

First things first, before we go any farther, please tell me the EXACT Denso part number you purchased for upstream and downstream and where you purchased it from.

I'm confused, you said you used Denso brand sensors, then said you installed TRQ sensors, after using scAmazon sensors, so I'm super confused. Please tell us what all four sensors are and the part numbers

Second, I'm also confused, what's up with the shifter in the background? This is a 2001 V8 Tundra with a manual floor shifter?

Third, you've said it's a 2001, but you have a 2004 Tundra and 2004 Sequoia showing in your truck info. Are any of these typos?

Fourth, the readout you're showing is weird for a 4.7L V8. Your truck should have four O2 sensors:

• B1S1 (driver upstream)
• B1S2 (driver downstream)
• B2S1 (passenger upstream)
• B2S2 (passenger downstream)

You're getting N/A data from your passenger side upstream/downstream sensors. Why?
And if you scroll up, are you seeing output on B1S1?

​

 

You confused @Martini8875 and @JeffTundraSR5Guy
V6 Manuel by the looks of it. V6 only has one front and one rear O2 sensor.

 

Got it. This is why I really don't like when people hijack other people's threads intead of creating their own. Thanks for helping me see that, @455h0le_dachshund

 

@Martini8875 can you tell us what EXACT part numbers did you buy?

I'm asking because on the upstream sensor, if you have auto transmission your part number should've ended in 9001. If you have manual transmission it should've ended in 9003. With the downstream sensor, your part number should've ended in 4161, regardless whether you're 2WD or 4WD. I'm assuming that part may've been different at one point, because Denso is splitting them apart in their part lookup tool. Hopefully you didn't get the "universal" downstream sensor with part number that ends in 4206.

If you bought the wrong upstream sensor, I could see it potentially causing this issue.

If you bought the sensor from an outlet known to sell fake/grey market parts like scAmazon or fleaBay, I can also see that potentially being the problem.

 

the part number I bought was 234-9003 for my upstream o2 sensor, but yes, I did buy from Amazon ‍♂️. I did look up the company that sold it on Amazon though and it’s a wholesale parts distributor out here in Anaheim…after installing, I never got another CEl, however clearly it isn’t pulling voltage.
Also, yes, mine is a v6 standard 04 tundra.
Apologies for hijacking the thread…I thought you just hop onto a thread that people seem to be talking on because when I’ve started a new thread in the past, someone always refers me to a previous thread and I never get an answer ‍♂️…thank you for the help though as well, I’m going to purchase another upstream from AutoZone and see if that will help.
Also another quick question…do I HAVE to disconnect my ground when installing? I just don’t want to have to complete all the drive cycles again…

 

Disconnecting negative batt cable for 5-10 mins during install is always advised to avoid accidental short/spark, and also to force-reset the vehicle’s ECU. If you’re throwing new hardware at it, but it learned to work with the old hardware, you may end up with sketch results. Resetting the ECU’s learned behavior helps counter that, and honestly it should reach readiness much sooner than 1k miles.

I’d be shocked if the case, but it’s entirely possible you got a bad part originally. Super rare, if it’s the case, but shit happens.

 

Got it, yea I just returned the Denso one from Amazon and I’m going to purchase the one from AutoZone and install tomorrow. It looks like it’s the bank 1 sensor right as in the upstream one?

 

I'm not sure because it's missing completely from the screen, as if you need to arrow up on the device.

Look at that last screen cap. Ignore the "O2" prefix on each line. The "B" number is the bank. "S" number is the sensor.

B1 = 1st bank.
S1 = 1st sensor (upstream)
S2 = 2nd sensor (downstream)

Notice you aren't even showing B1S1, so I can't tell you if the voltage reading or any other reading on it is correct. With that scanner, not only should be be able to see it, but see readings other than voltage.

 

Oh shit, I see it now, it's on the screen just before that.

Did you try unplugging and replugging the upstream connector, checking both the connector and sensor wire for bent pins?

 

You're good. Old man @shifty` can be a little grouchy sometimes, but he's a wealth of knowledge.

 

I haven’t just yet, I’m just going to replace the whole sensor with one from AutoZone so I know it’s “real”
I will update tomorrow after I run the diag and all that. Thank you again. Very very helpful!

 

So I changed the upstream sensor to a brand new Denso from AutoZone…I’m still not having a voltage read for the B1S1 sensor… not sure what to do now

 

Start tracing wiring. I'd start with grounds. Do you happen to live in a road salt state?

 

Okay I’ll start checking…nope, California and the truck has been here its whole life too. Had it for 20 years. Just passed smog in 2022 but won’t pass in 2023 ‍♂️